restoreCheckpoint hard-resets the worktree with no safety checkpoint first

[currentbits]

Problem

electron/worktrees.js:2522-2526 runs git reset --hard <sha> directly when restoring a checkpoint. maybeCreateCheckpoint (worktrees.js:2393-2429) exists and is exactly the right safety net, but it is not invoked before the reset.

Impact

Any uncommitted work in the thread worktree (manual edits the user made in that folder, or changes from a run whose post-turn checkpoint silently failed, which is best-effort by design) is destroyed unrecoverably by one click on an older checkpoint.

Fix direction

Attempt maybeCreateCheckpoint(store, threadId) before the reset. One-line change plus a test.