feat(web): add mobile sidebar swipe actions

[Pearcekieser]

Closes #9148

What Changed

• Added a mobile-width left-swipe gesture to active and pinned web sidebar thread cards.
• Reveals capability-aware Settle, Snooze, and Pin/Unpin touch actions.
• Reuses the existing settle, snooze preset, pin, and unpin command paths.
• Keeps one tray open at a time and clears it when the mobile sidebar closes.
• Added direction locking that favors vertical scrolling for ambiguous gestures.
• Translates only the inner row surface, preserving list height and auto-animate geometry.
• Documented the mobile web interaction in the thread sidebar user guide.

No server contracts or native mobile code changed.

Why

The desktop sidebar exposes quick actions through hover, but phone browsers have no hover. Common
thread-triage actions therefore require extra menu navigation on mobile web.

This adds a familiar Mail-style touch interaction while keeping lifecycle behavior in the existing
action implementations. The gesture code is isolated from sorting and list layout to reduce
conflicts with current pinned reordering and the active-thread reorder work in #8666.

UI Changes

Before	After

Gesture progress

The screenshots were captured at a 430 × 932 CSS-pixel viewport with a disposable, synthetic T3
environment. The temporary Playwright artifact test also asserts that the row remains translated
-216px after pointer-up and that exactly one Settle, Snooze, and Pin action exists for the target
row.

During visual verification, the test caught a post-pointer-up synthetic click that initially closed
the freshly opened tray. Click suppression now consumes that event without changing the tray's open
state.

Verification

• vp test run apps/web/src/components/Sidebar.swipe.test.ts --passWithNoTests
  • 8 tests passed.
• tsgo -p apps/web/tsconfig.json --noEmit
• Targeted lint passed for:
  • apps/web/src/components/Sidebar.tsx
  • apps/web/src/components/SidebarSwipeActions.tsx
  • apps/web/src/components/Sidebar.swipe.ts
  • apps/web/src/components/Sidebar.swipe.test.ts
• Formatting and git diff --check passed.
• Disposable Playwright artifact test passed at mobile viewport and produced the screenshots above.

Surface coverage

• Entry points: The gesture is an additional mobile sidebar entry point; context menus and chat
  header actions remain unchanged.
• Clients: Mobile-width web is changed. Desktop retains existing hover behavior. Native iOS and
  Android are unchanged.
• Providers: Provider-independent; actions use environment capability flags and shared thread
  commands.
• Contracts: No changes.
• Reverse states: Pinned cards show Unpin; existing snooze and settle reversal flows remain
  available.
• Connection modes: Uses the existing per-environment command routing for local, remote, relay,
  and tunnel connections.
• Docs: Updated docs/user/thread-sidebar.md.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for UI changes
• I included a video for animation/interaction changes

Built by GPT-5.6 Sol via the Codex harness in T3 Code.

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR introduces a substantial mobile swipe interaction with new Settle, Snooze, and Pin/Unpin action workflows, while changing pointer and click behavior in the shared production sidebar. Its automatic activation for mobile users and broad interaction surface warrant human review despite reusing existing server commands and contracts.

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[Pearcekieser]

Closing this PR following the direction on #9148 to discuss the mobile-web swipe proposal in Ideas first. The implementation and evidence remain available here for reference; this is not being merged.