[Bug]: Removing worktree breaks thread when checking out branch elsewhere

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Related to https://github.com/pingdotgg/t3code/pull/7839

Area

apps/server

Steps to reproduce

1. Main project: cd ~/path/to/project
2. git worktree add ~/path/to/project-worktrees/feature/some-feature feature/some-feature
3. Thread in Worktree
4. git worktree remove ~/path/to/project-worktrees/feature/some-feature
5. git checkout feature/some-feature
6. Send message in thread

Expected behavior

7. Switch to the main project or a worktree that has the branch or otherwise to the main project?

Actual behavior

7. VCS process failed in GitVcsDriver.initRepository: git (/Users/user/path/to/project-worktrees/feature/some-feature) exited with 128 - Process exited with a non-zero status.

Impact

Major degradation or frequent failure

Version or commit

0.0.35-nightly.20260826.1194

Environment

No response

Logs or stack traces

Screenshots, recordings, or supporting files

Workaround

7. git switch off of feature/some-feature
8. Send message in thread
9. T3Code recreates the worktree
10. Within T3Code: switch to a branch that's checked out elsewhere to leave the worktree
11. Remove the worktree
12. git switch feature/some-feature

Start in apps/server and reproduce the listed git worktree removal and branch checkout sequence. Then inspect GitVcsDriver.initRepository and trace how the removed worktree path is handled when a thread sends a message. Done means the thread can continue without the failed VCS process, using the main project or an available worktree as appropriate.