fix: Discord embed polish — resize handles, gesture freeze, auto zoom, compact mode

[nishant]

Summary

Phase A of the Discord-widget rework: three defects fixed on top of the (unchanged, load-bearing) app-lifetime DiscordHost architecture.

1. Dead resize handles → padded frame

RGL renders handle spans INSIDE each grid item; grid items are transform-created stacking contexts, so no handle could rise above the root-level fixed z-30 host — every handle under the webview (s/se/sw/e/w) was dead. The tile body now wraps a p-2 gutter and publishes the INNER div's rect, exposing RGL's edge/corner hit areas all around the webview and letting the tile chrome visibly frame the embed. Host corners: rounded-b-md → rounded-md (all four are visible inside the gutter).

2. Resize/drag jank → gesture freeze + settle debounce

New ephemeral discordStore.interacting, set/cleared by DashboardGrid's onDragStart/onResizeStart/onDragStop/onResizeStop (any tile's gesture — harmless when Discord isn't visible). While interacting: host position tracks per frame, width/height FREEZE at the last settled size, and the host goes pointer-events:none so grid mousemoves never hit the guest. Final size applies once on gesture end; out-of-gesture size changes (window resize) settle via a 120 ms trailing debounce. Decision logic is the pure helper nextHostStyle(rect, interacting, settledSize) in apps/renderer/src/widgets/discord/lib.ts — unit-tested.

3. Scaling — auto zoom + compact CSS + dark splash

• zoomForWidth(width): ≥900px → 1.0, ≥700 → 0.9, ≥550 → 0.85, else 0.75 — applied on webview dom-ready, re-applied only on settled-width breakpoint crossings and after reload. setZoomFactor(factor): void / insertCSS(css): Promise<string> added to DiscordWebviewElement, pinned against electron@33.4.11 WebviewTag typings.
• DISCORD_COMPACT_CSS hides the members list ([class*="membersWrap"]) on every dom-ready (inserted CSS doesn't survive navigation). FAIL-SOFT: selector rot = stock layout, nothing breaks. Server rail + channel sidebar deliberately kept.
• Loading splash is now Discord's own dark (#313338) — no theme-colored flash.

Out of scope / follow-ups

• No settings toggle for compact mode in this PR — Settings files are owned by another in-flight agent; a "hide members list" toggle can follow.
• layoutStore, SettingsModal, IPC/preload untouched; DashboardGrid edits are limited to the gesture callbacks.

Gates

• pnpm test green (renderer suite incl. 8 discord lib tests), pnpm typecheck green, pnpm lint green — re-run after rebasing onto master @ feat: accordion expand takes space from the widget below instead of reflowing the grid #122.

Verification for Nish (needs the running app — not covered by unit tests)

1. All eight resize handles on the Discord tile should now respond (previously only n/ne/nw).
2. Drag/resize any tile: the Discord webview should hold its size during the gesture (position follows), snap to final size on release — no per-mousemove relayout tearing.
3. Shrink the tile below ~900/700/550px widths: Discord should step down in zoom; members list should be hidden at all widths (fail-soft if Discord renamed the class).
4. Reload button: compact CSS + zoom re-apply after reload.
5. Splash on first load is Discord-dark, not white.
6. Regression check: layout switch away/back keeps you signed in + in voice (host architecture untouched).

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