fix(app): unify session project icon resolution

[opencode-agent]

Summary

• Resolve session project avatars from enriched opened-project data, falling back to synced project metadata when a project isn't open. Home session rows/search, command-palette session search, titlebar tabs, and the session header share the resolver.
• Merge the selected enriched project's name and icon into canonical synced project metadata in the server context before rendering desktop/mobile session details. The details panel receives one project, without separate avatar accessors/props; its ID, canonical worktree, worktree inventory, and workspace-menu destinations stay intact.
• Fix the nested-project mismatch: when /documents and /documents/project are both added, an opened ancestor previously won the first-containing-directory fallback while the child ID was loading. A stored child project ID now beats an unrelated opened ancestor; an exact opened child can supply its icon when stored metadata confirms its canonical directory. Exact opened worktree matches beat ancestor sandbox entries.

Verification

• bun typecheck in packages/app — pass
• Existing focused app unit tests (helpers.test.ts, records.test.ts) — 25 pass. No test changes are included, per request.
• Command palette browser-condition unit tests — 2 pass
• Scoped oxlint, git diff --check, production Vite build — pass
• Full bun run check is blocked outside this change: the Host has Node 18, while Astro in @opencode/www requires Node >=22.12.
• Attempted the same production-build warm-tab benchmark before and after; both fail before collecting metrics because the existing mock session route returns ClientError: UnsupportedContentType. The focused browser summary test hit the same pre-existing fixture failure, so no passing browser or performance result is claimed.

Requested by: @Brendonovich (Brendan via Slack)