feat(desktop): add LAN mobile remote control

[AlexZander85]

Issue for this PR

Related to #10288

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds LAN-only remote control for an existing OpenCode Desktop session.

From the session header, the user can open Remote Control, scan a QR code with a phone on the same local network, and control that session through a session-scoped mobile interface.

The remote interface supports:

• viewing visible session messages and status
• sending text prompts
• aborting the current run
• answering permission requests
• answering questions

The implementation intentionally does not expose the full sidecar API, terminal access, filesystem access, or Internet/relay access.

Pairing uses a short-lived one-time ticket which is exchanged for a revocable session-scoped grant. The Desktop LAN gateway only proxies /remote/*.

This is a draft PR mainly to get feedback on whether this narrower LAN-only approach fits the project direction.

How did you verify your code works?

Added targeted unit/integration coverage for pairing, session-scoped authorization, cross-session rejection, bootstrap/event filtering, text-only prompts, revoke/session deletion, pairing lifecycle races, LAN address changes, and gateway boundaries.

Also ran a browser-level Chromium/Playwright smoke test of the production mobile UI covering pairing, permission reply, question reply, sending a prompt, live refresh, and stop/abort.

The browser flow completed without page errors. Physical phone-to-Desktop LAN testing and upstream CI are still pending.

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Hey! Your PR title Remote control doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍