P1: Worktree removal deletes untracked files when status.showUntrackedFiles=no #1519

Data loss. The fast worktree-removal path checks cleanliness with plain git status --porcelain (electron/worktrees-lifecycle.js:176). That honours the user's status.showUntrackedFiles config: with no, untracked files are hidden, st.stdout is empty, and the directory is renamed to .trash-* and deleted asynchronously (:185-194). The agent's uncommitted new files are gone.

Fix (S): run the check as git -c status.showUntrackedFiles=normal status --porcelain (or --untracked-files=normal). Audit any other "is it clean?" check that gates a destructive action (cleanup, GC, merged-worktree reclaim in worktrees-gc.js) for the same pattern.

Test: a repo with git config status.showUntrackedFiles no plus one untracked file in the worktree. Removal without force must refuse.