# Implementation: fix-stale-task-mtime-proxy

## Bug
`--can-edit` used `.state` file mtime as a proxy for "last edit activity" to detect stale tasks. But `.state` is modified by phase transitions, not by actual editing. A task in `implement` phase for 30+ minutes would be flagged as stale even if the developer was actively editing files the whole time, because `.state` mtime only reflects the last phase transition.

## Fix
1. Added `_get_edit_timestamp()` — reads `.state.lastedit` mtime if it exists, falls back to `.state` mtime for backward compatibility
2. Added `_touch_lastedit()` — creates/updates `.state.lastedit` file
3. `--can-edit` now calls `_touch_lastedit()` on ALLOWED responses (both project-level and task-level paths), recording actual edit activity
4. Staleness check uses `_get_edit_timestamp()` instead of raw `.state` mtime
5. Added `.state.lastedit` to `NON_ARTIFACT_FILES` so it's not treated as a phase artifact
6. `--same-session` uses `_get_edit_timestamp()` for consistent activity tracking
7. `--touch` command now touches `.state.lastedit` instead of `.state`
8. Added staleness check to the single-task `--can-edit --task` path (previously only project-level `--can-edit` checked staleness)

## Files Changed
- `scripts/status.py`: Added `_get_edit_timestamp()`, `_touch_lastedit()`, updated `cmd_can_edit()`, `cmd_same_session()`, `cmd_touch()`, `NON_ARTIFACT_FILES`
- `tests/test_status.py`: Added `TestStateLastEdit` class with 5 tests and `TestTestPlanPhaseMapping` class

## Tests
- `test_can_edit_creates_lastedit_on_allowed`: Verifies `.state.lastedit` is created on ALLOWED
- `test_can_edit_creates_lastedit_with_file_scope`: Same for file-scoped can-edit
- `test_stale_uses_lastedit_not_state_mtime`: Old `.state` + recent `.state.lastedit` → not stale
- `test_stale_when_lastedit_old`: Recent `.state` + old `.state.lastedit` → stale
- `test_falls_back_to_state_mtime_without_lastedit`: No `.state.lastedit` → falls back to `.state` mtime
- All 249 tests pass