feat(intelligence): add Memory Timeline

app/src/components/intelligence/MemoryTimelinePanel.test.tsx

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+import { fireEvent, render, screen } from '@testing-library/react';
+import { describe, expect, it, vi } from 'vitest';
+
+import { computeTimeline } from '../../lib/memory/memoryTimeline';
+import type { GraphRelation } from '../../utils/tauriCommands/memory';
+import MemoryTimelinePanel from './MemoryTimelinePanel';
+
+const NOW = 1_700_000_000;
+
+function utc(year: number, month: number, day = 1): number {
+  return Math.floor(Date.UTC(year, month - 1, day) / 1000);
+}
+
+function rel(updatedAt: number): GraphRelation {
+  return {
+    namespace: 'n',
+    subject: 'You',
+    predicate: 'p',
+    object: 'x',
+    attrs: {},
+    updatedAt,
+    evidenceCount: 1,
+    orderIndex: null,
+    documentIds: [],
+    chunkIds: [],
+  };
+}
+
+const report = computeTimeline(
+  [rel(utc(2023, 1, 10)), rel(utc(2023, 1, 20)), rel(utc(2023, 3, 5))],
+  NOW
+);
+
+describe('<MemoryTimelinePanel />', () => {
+  it('renders the loading skeleton', () => {
+    render(<MemoryTimelinePanel report={null} loading />);
+    expect(screen.getByTestId('memory-timeline-loading')).toBeInTheDocument();
+  });
+
+  it('renders the empty state when there are no facts', () => {
+    render(<MemoryTimelinePanel report={computeTimeline([], NOW)} />);
+    expect(screen.getByText('No knowledge graph yet.')).toBeInTheDocument();
+  });
+
+  it('renders an error with a working retry button', () => {
+    const onRetry = vi.fn();
+    render(<MemoryTimelinePanel report={null} error="graph unavailable" onRetry={onRetry} />);
+    expect(screen.getByRole('alert').textContent).toMatch(/graph unavailable/);
+    fireEvent.click(screen.getByRole('button', { name: 'Retry' }));
+    expect(onRetry).toHaveBeenCalledTimes(1);
+  });
+
+  it('renders summary tiles, the busiest caption, and per-month bars', () => {
+    render(<MemoryTimelinePanel report={report} />);
+    expect(screen.getByText('Facts')).toBeInTheDocument();
+    expect(screen.getByText('Active months')).toBeInTheDocument();
+    expect(screen.getByText('Last 30 days')).toBeInTheDocument();
+    expect(screen.getByText('Facts learned per month')).toBeInTheDocument();
+    expect(screen.getByText('2023-01')).toBeInTheDocument();
+    expect(screen.getByText('2023-03')).toBeInTheDocument();
+    expect(screen.getByText('Busiest: 2023-01 (2)')).toBeInTheDocument();
+  });
+
+  it('notes undated facts when present', () => {
+    const withUndated = computeTimeline([rel(utc(2023, 5, 1)), rel(0), rel(0)], NOW);
+    render(<MemoryTimelinePanel report={withUndated} />);
+    expect(screen.getByText('2 fact(s) have no recorded date.')).toBeInTheDocument();
+  });
+});

app/src/components/intelligence/MemoryTimelinePanel.tsx

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+/**
+ * Memory Timeline — presentational view. Pure: renders the per-month fact
+ * histogram + summary tiles. No data fetching, no clock, no RNG.
+ */
+import { useT } from '../../lib/i18n/I18nContext';
+import type { TimelineReport } from '../../lib/memory/memoryTimeline';
+
+const MAX_BARS = 24;
+
+interface MemoryTimelinePanelProps {
+  report: TimelineReport | null;
+  loading?: boolean;
+  error?: string | null;
+  onRetry?: () => void;
+}
+
+const MemoryTimelinePanel = ({ report, loading, error, onRetry }: MemoryTimelinePanelProps) => {
+  const { t } = useT();
+
+  const intro = (
+    <div
+      role="note"
+      className="rounded-lg border border-primary-200 dark:border-primary-500/30 bg-primary-50 dark:bg-primary-500/10 px-3 py-2 text-xs text-stone-700 dark:text-neutral-200">
+      <p className="font-medium mb-1">{t('memoryTimeline.title')}</p>
+      <p>{t('memoryTimeline.intro')}</p>
+    </div>
+  );
+
+  if (loading) {
+    return (
+      <div className="space-y-4">
+        {intro}
+        <div
+          className="space-y-3"
+          role="status"
+          aria-label={t('memoryTimeline.loading')}
+          data-testid="memory-timeline-loading">
+          <div className="grid gap-2 sm:grid-cols-3">
+            {[0, 1, 2].map(i => (
+              <div
+                key={i}
+                className="animate-pulse rounded-lg border border-stone-200 dark:border-neutral-800 bg-stone-50 dark:bg-neutral-800/60 h-16"
+              />
+            ))}
+          </div>
+          {[0, 1, 2, 3].map(i => (
+            <div
+              key={i}
+              className="animate-pulse rounded-lg border border-stone-200 dark:border-neutral-800 bg-stone-50 dark:bg-neutral-800/60 h-6"
+            />
+          ))}
+        </div>
+      </div>
+    );
+  }
+
+  if (error) {
+    return (
+      <div className="space-y-4">
+        {intro}
+        <div className="rounded-lg border border-coral-200 dark:border-coral-500/30 p-4 text-center">
+          <p role="alert" className="text-xs text-coral-700 dark:text-coral-300">
+            {t('memoryTimeline.errorPrefix')} {error}
+          </p>
+          {onRetry && (
+            <button
+              type="button"
+              onClick={onRetry}
+              className="mt-2 rounded-lg bg-primary-500 px-3 py-1.5 text-xs font-semibold text-white hover:bg-primary-600">
+              {t('memoryTimeline.retry')}
+            </button>
+          )}
+        </div>
+      </div>
+    );
+  }
+
+  if (!report || (report.total === 0 && report.undated === 0)) {
+    return (
+      <div className="space-y-4">
+        {intro}
+        <div className="py-8 text-center">
+          <h3 className="text-sm font-semibold text-stone-700 dark:text-neutral-200">
+            {t('memoryTimeline.empty')}
+          </h3>
+          <p className="mt-1 text-xs text-stone-500 dark:text-neutral-400">
+            {t('memoryTimeline.emptyHint')}
+          </p>
+        </div>
+      </div>
+    );
+  }
+
+  const maxCount = report.busiest?.count ?? 1;
+  const shown = report.buckets.slice(-MAX_BARS);
+  const truncated = report.buckets.length > MAX_BARS;
+
+  return (
+    <div className="space-y-4">
+      {intro}
+
+      {/* Summary tiles */}
+      <div className="grid gap-2 sm:grid-cols-3">
+        {[
+          { label: t('memoryTimeline.metricTotal'), value: report.total },
+          { label: t('memoryTimeline.metricMonths'), value: report.buckets.length },
+          { label: t('memoryTimeline.metricRecent'), value: report.recentCount },
+        ].map(tile => (
+          <div
+            key={tile.label}
+            className="rounded-lg border border-stone-200 dark:border-neutral-800 p-3">
+            <div className="text-[10px] uppercase tracking-wider text-stone-400 dark:text-neutral-500">
+              {tile.label}
+            </div>
+            <div className="text-lg font-semibold tabular-nums text-stone-900 dark:text-neutral-100">
+              {tile.value}
+            </div>
+          </div>
+        ))}
+      </div>
+
+      {report.busiest && (
+        <p className="text-[11px] text-stone-500 dark:text-neutral-400 tabular-nums">
+          {t('memoryTimeline.busiestCaption')
+            .replace('{period}', report.busiest.period)
+            .replace('{count}', String(report.busiest.count))}
+        </p>
+      )}
+
+      {/* Per-month histogram */}
+      {shown.length > 0 && (
+        <section aria-labelledby="memory-timeline-heading" className="space-y-1">
+          <h3
+            id="memory-timeline-heading"
+            className="text-xs font-semibold uppercase tracking-wider text-stone-500 dark:text-neutral-400">
+            {t('memoryTimeline.heading')}
+          </h3>
+          <ul className="space-y-1">
+            {shown.map(bucket => (
+              <li key={bucket.period} className="flex items-center gap-2 text-[11px] tabular-nums">
+                <span className="w-16 shrink-0 text-stone-400 dark:text-neutral-500">
+                  {bucket.period}
+                </span>
+                <div className="flex-1 h-3 rounded bg-stone-100 dark:bg-neutral-800 overflow-hidden">
+                  <div
+                    className="h-full bg-primary-400/70"
+                    style={{ width: `${(bucket.count / maxCount) * 100}%` }}
+                  />
+                </div>
+                <span className="w-8 shrink-0 text-right text-stone-500 dark:text-neutral-400">
+                  {bucket.count}
+                </span>
+              </li>
+            ))}
+          </ul>
+          {truncated && (
+            <p className="text-center text-xs text-stone-400 dark:text-neutral-500">
+              {t('memoryTimeline.truncated')
+                .replace('{shown}', String(shown.length))
+                .replace('{total}', String(report.buckets.length))}
+            </p>
+          )}
+        </section>
+      )}
+
+      {report.undated > 0 && (
+        <p className="text-[11px] text-stone-400 dark:text-neutral-500">
+          {t('memoryTimeline.undatedNote').replace('{count}', String(report.undated))}
+        </p>
+      )}
+    </div>
+  );
+};
+
+export default MemoryTimelinePanel;

app/src/components/intelligence/MemoryTimelineTab.test.tsx

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+import { fireEvent, render, screen, waitFor } from '@testing-library/react';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+import { computeTimeline } from '../../lib/memory/memoryTimeline';
+import type { GraphRelation } from '../../utils/tauriCommands/memory';
+import MemoryTimelineTab from './MemoryTimelineTab';
+
+const mockLoadTimeline = vi.fn();
+const mockLoadNamespaces = vi.fn();
+
+vi.mock('../../services/api/memoryTimelineApi', () => ({
+  loadTimeline: (...args: unknown[]) => mockLoadTimeline(...args),
+  loadNamespaces: (...args: unknown[]) => mockLoadNamespaces(...args),
+}));
+
+const NOW = 1_700_000_000;
+
+function rel(updatedAt: number): GraphRelation {
+  return {
+    namespace: 'n',
+    subject: 'You',
+    predicate: 'p',
+    object: 'x',
+    attrs: {},
+    updatedAt,
+    evidenceCount: 1,
+    orderIndex: null,
+    documentIds: [],
+    chunkIds: [],
+  };
+}
+
+const report = computeTimeline([rel(Math.floor(Date.UTC(2023, 0, 10) / 1000))], NOW);
+
+describe('<MemoryTimelineTab />', () => {
+  beforeEach(() => {
+    mockLoadTimeline.mockReset();
+    mockLoadNamespaces.mockReset();
+    mockLoadTimeline.mockResolvedValue(report);
+    mockLoadNamespaces.mockResolvedValue([]);
+  });
+
+  it('loads the timeline on mount and renders it', async () => {
+    render(<MemoryTimelineTab />);
+    expect(mockLoadTimeline).toHaveBeenCalledTimes(1);
+    expect(mockLoadTimeline.mock.calls[0][1]).toBeUndefined(); // (nowSeconds, undefined-namespace)
+    await waitFor(() => expect(screen.getByText('Facts learned per month')).toBeInTheDocument());
+  });
+
+  it('shows the namespace selector and re-queries on change', async () => {
+    mockLoadNamespaces.mockResolvedValueOnce(['work', 'personal']);
+    render(<MemoryTimelineTab />);
+    await waitFor(() => screen.getByRole('combobox'));
+    fireEvent.change(screen.getByRole('combobox'), { target: { value: 'work' } });
+    await waitFor(() => expect(mockLoadTimeline).toHaveBeenCalledTimes(2));
+    expect(mockLoadTimeline.mock.calls[1][1]).toBe('work');
+  });
+
+  it('surfaces an error when the load fails', async () => {
+    mockLoadTimeline.mockReset();
+    mockLoadTimeline.mockRejectedValueOnce(new Error('graph unavailable'));
+    render(<MemoryTimelineTab />);
+    await waitFor(() => expect(screen.getByRole('alert').textContent).toMatch(/graph unavailable/));
+  });
+});

app/src/components/intelligence/MemoryTimelineTab.tsx

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+/**
+ * Memory Timeline tab (container). Load-on-mount, namespace selector, and mints
+ * `nowSeconds` (in handlers, never during render) for the recency window.
+ * Delegates rendering to the pure <MemoryTimelinePanel>. Read-only.
+ */
+import { useCallback, useEffect, useRef, useState } from 'react';
+
+import { useT } from '../../lib/i18n/I18nContext';
+import type { TimelineReport } from '../../lib/memory/memoryTimeline';
+import { loadNamespaces, loadTimeline } from '../../services/api/memoryTimelineApi';
+import MemoryTimelinePanel from './MemoryTimelinePanel';
+
+const nowSeconds = (): number => Math.floor(Date.now() / 1000);
+
+const MemoryTimelineTab = () => {
+  const { t } = useT();
+  const [report, setReport] = useState<TimelineReport | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+  const [namespaces, setNamespaces] = useState<string[]>([]);
+  const [namespace, setNamespace] = useState('');
+  // Monotonic token: ignore a response if a newer load has since started.
+  const latestRequestId = useRef(0);
+
+  const load = useCallback(async (ns: string) => {
+    const requestId = (latestRequestId.current += 1);
+    setLoading(true);
+    setError(null);
+    try {
+      const next = await loadTimeline(nowSeconds(), ns || undefined);
+      if (requestId !== latestRequestId.current) return;
+      setReport(next);
+    } catch (err) {
+      if (requestId !== latestRequestId.current) return;
+      setError(err instanceof Error ? err.message : String(err));
+    } finally {
+      if (requestId === latestRequestId.current) setLoading(false);
+    }
+  }, []);
+
+  useEffect(() => {
+    loadNamespaces()
+      .then(setNamespaces)
+      .catch(() => setNamespaces([]));
+    void load('');
+  }, [load]);
+
+  const handleNamespace = (next: string): void => {
+    setNamespace(next);
+    void load(next);
+  };
+
+  return (
+    <div className="space-y-4">
+      {namespaces.length > 0 && (
+        <label className="flex items-center gap-2 text-xs text-stone-600 dark:text-neutral-300">
+          {t('memoryTimeline.namespaceLabel')}
+          <select
+            value={namespace}
+            onChange={e => handleNamespace(e.target.value)}
+            className="rounded-lg border border-stone-200 dark:border-neutral-700 bg-white dark:bg-neutral-900 px-2 py-1 text-sm text-stone-800 dark:text-neutral-100">
+            <option value="">{t('memoryTimeline.namespaceAll')}</option>
+            {namespaces.map(ns => (
+              <option key={ns} value={ns}>
+                {ns}
+              </option>
+            ))}
+          </select>
+        </label>
+      )}
+
+      <MemoryTimelinePanel
+        report={report}
+        loading={loading}
+        error={error}
+        onRetry={() => void load(namespace)}
+      />
+    </div>
+  );
+};
+
+export default MemoryTimelineTab;