## What changed
- Add a configurable `new_worktree` action, bound to `w`, for local sessions with worktree support enabled.
- Create the worktree from the cached project default branch, preferring remote `HEAD` and falling back to conventional `main` or `master` refs without fetching. Preserve the selected subdirectory and source checkout edits.
- Start and bind a blank session in the new worktree, preserving the selected approval reviewer without sending an initial turn.
- Show creation progress, pause conflicting actions, clean up unclaimed clean worktrees, and report retained checkout paths when session startup fails. Clear pending creation state on reconnect.
## Testing
Add coverage for default-branch selection, source checkout preservation, session ownership and approval settings, cleanup, startup failures, reconnect state, and busy-state rendering. Extend Git environment isolation coverage and test unrelated non-UTF-8 refs.
GitOrigin-RevId: 771ddc12d04dbf0d12e77e9c96c8386cf31e67c5
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