Git Worktrees for Parallel Agents

In Cloudroom (`$ROOM_THREAD_ID` is set)

Never run git worktree add yourself. Cloudroom only deletes worktrees it made, so hand-made ones pile up in ~/code forever.

New task: start the thread with New worktree instead.
Move this thread to its own worktree: fork it into a Cloudroom-managed worktree. Cloudroom makes the branch and deletes the folder once its last thread is archived (after the worktree retention setting, default 30 days).
```
room-cli thread fork "$ROOM_THREAD_ID" --new-environment worktree --title "<task>" \
  --prompt "You now run in a new worktree. Copy the gitignored .env files from <primary checkout> into it, then stop and wait for the user."
```
It branches from main, so uncommitted edits stay behind; commit them first or pass --base-branch <ref>. Then tell the user to continue in the new thread and archive this one. Skip the rest of this skill.

Detect where you are before editing: