feat: add pinned chats

[mshykhov]

Summary

• add Pin chat / Unpin chat to the existing chat actions sheet
• render pinned chats once in a dedicated section above project groups
• persist pinned thread IDs locally so pins survive app restarts
• show the workspace leaf folder and relative activity time on pinned rows

Behavior

• newly pinned chats are placed first; repeated pin/unpin operations are idempotent
• pinned chats are removed from their normal project group to avoid duplicate rows
• search keeps the existing flat project results and does not render a separate pinned section
• duplicate and missing persisted thread IDs are ignored safely
• archiving a chat also removes its pinned state after a successful archive
• only the final workspace folder is displayed; long metadata stays on one line with middle ellipsis
• pin state is device-local and is not synced through the Relay server

Implementation

• pinned-thread-store.ts uses the existing Legend State persistence helper
• thread-drawer-rows.ts builds stable, unique drawer rows and preserves collapsed-project behavior
• ThreadDrawerContent.tsx composes the existing bottom sheet action and renders pinned metadata
• focused tests cover persistence, ordering, duplicate IDs, search behavior, active rows, and workspace labels

Screenshots

Pin action	Unpin action	Pinned after cold restart

Validation

• corepack pnpm --filter codex-relay test - 290 passed, 4 skipped
• corepack pnpm -r typecheck
• corepack pnpm exec oxlint apps packages --import-plugin --react-plugin --jsx-a11y-plugin --vitest-plugin
• corepack pnpm exec oxfmt . --check
• Android emulator: pin, unpin, workspace label, and persistence after a cold restart
• GitHub CI: Lint, format, and typecheck passed

Release

• adds a patch changeset for @codex-relay/mobile

Closes #58

Out of scope

• collapsing and expanding the Pinned section; it stays visible whenever pinned chats exist and can be added as a focused follow-up

[changeset-bot]

🦋 Changeset detected

Latest commit: aaca3b0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@codex-relay/mobile	Patch

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