- Move BranchToolbar below the chat input box to match Codex app layout
- Change worktree path to ~/.t3code/worktrees/{repo}/{branch}
- Split desktop tsdown config into separate main/preload builds to prevent
  code-splitting from leaking node:os into the sandboxed preload script
- Migrate turbo scripts to turbo watch, add desktop start/smoke-test tasks
- Update server output to .mjs, add CJS format, remove tsx dependency

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>