Xp history chart sparkline on agent detail page using 7 day xp snapshots

[clintjeff2]

Motivation

• Provide a compact visual of recent XP growth on the agent detail page using the persisted XP history endpoint.
• Show daily earned XP over the last 7 days (pad with zeros when history is shorter), current level, total XP, and progress to the next level.
• Use a lightweight approach (small helper + SVG sparkline) to avoid pulling a new chart dependency and to prevent layout shift by reserving fixed height.

Description

• Add lib/agents/xp-history-chart.ts with buildSevenDayXpSnapshots(events, now) to aggregate earned XP into seven UTC daily snapshots and getLevelProgress(totalXp, level) to compute bounded progress percentages.
• Update app/agents/[id]/page.tsx to fetch GET /api/agents/[id]/xp/history, derive totalXp, level, xpToNext, compute snapshots and progress, and render an XP Growth card with a level Badge, total XP, XP-to-next display, a progress bar, and a fixed-height SVG XpSparkline.
• Implement the sparkline as an inline SVG that renders seven labeled points, an area fill, and tooltips, ignoring decay events when aggregating "earned" XP.
• Add unit tests lib/agents/xp-history-chart.test.ts covering padding for <7 days, exactly 7-day aggregation, decay-event exclusion, and bounded progress calculation.

Testing

• Ran ESLint on the changed files with npx eslint 'app/agents/[id]/page.tsx' lib/agents/xp-history-chart.ts lib/agents/xp-history-chart.test.ts and addressed a single unused-import warning.
• Ran unit tests with npm test -- --run lib/agents/xp-history-chart.test.ts and all tests passed (3 tests).
• Attempted production build with npm run build which failed in this environment because Next failed to fetch Google Fonts from fonts.googleapis.com.
• Ran type check npx tsc --noEmit which failed in this environment due to existing missing type dependencies (lru-cache, @wagmi/connectors).

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Closes #194

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[clintjeff2]

@leocagli, review and merge.