feat(desktop): type-to-focus the composer from empty chat chrome

[OutThisLife]

Summary

• Printable keys on empty chat chrome focus the composer and type the character (Discord/Slack-style).
• Soft / and Enter do the same when nothing else owns those keys; / opens the slash palette on an empty draft.
• Gated against dialogs, menus, terminals, full-page destinations, editables, and Enter-on-button activators. Bound shortcuts still win.

Test plan

• Click the transcript, type letters → composer focuses and text appears
• Click the transcript, press / → slash palette opens
• Click the transcript, press Enter → composer focuses (no send)
• Focus a button, press Enter → button activates (not composer)
• Open a dialog / command palette → / and typing stay local
• Focus the terminal → typing stays in the PTY
• Shift+N / ⌘K still fire their keybinds
• npx vitest run src/lib/keybinds/composer-focus-keys.test.ts (from apps/desktop)

[github-actions]

૮ >ﻌ< ა ci review

_{running on a1a406f}

CI timings

CI timings · View job

Wall time 7m42s vs 8m40s (-11.2%). 2 job(s) slower, 5 faster,

• Build&Test Docker image / build (arm64, ubuntu-24.04-arm, linux/arm64, type=gha,scope=docker-arm64, type=gha,mode=max,scope...: -42.0s
• Build&Test Docker image / build (amd64, ubuntu-latest, linux/amd64, type=gha,scope=docker-amd64, type=gha,mode=max,scope=do...: -31.0s
• Detect affected areas: -4.0s
• OSV scan / Scan lockfiles / osv-scan: +3.0s
• OSV scan / Emit review status: +1.0s