The undo ring is local working state, handled at all three
project-file seams (R13):
- .gitignore template ignores /.snapshots/
- export excludes .snapshots/ (like playground.db / history.log)
- safely_delete_temp_project allowlists .snapshots/ so a temp that
was modified then undone back to empty stays auto-deletable
- undo::SNAPSHOTS_DIR is now a pub const referenced by all three
- tests: gitignore content, export exclusion, cleanup allowlist
1693 passed / 0 failed / 1 ignored; clippy clean.
claude@clouddev1
d6c5674bf5