Archive completed tasks, add cleanup commands, self-documenting dashboard UI

- Archive 79 completed framework-dev tasks from tasks/ -> tasks/complete/
- status.py: add --cleanup-done and --install-cleanup-schedule commands
- Add scripts/automaton-cleanup.sh for periodic task archiving
- Dashboard: rename 'Background' tab -> 'Agent', 'Cleanup' agent -> 'Completed Task Archiver', remove redundant group headers and pill badges, dim inactive agent placeholders
- .rules.md: add Self-Documenting UI Names rule
- New tests: test_cleanup_done.py, expanded test_app.py and test_task.py

tasks/complete/plug-stale-task-hole/ADVERSARIAL_BUG_REPORT.md

@@ -0,0 +1,14 @@
+# Adversarial Bug Report — plug-stale-task-hole
+
+## Attack Vectors
+1. **Clock reset bypass**: Can an attacker manipulate the activity clock to bypass stale detection?
+2. **False positives**: Can legitimate activity be misclassified as stale?
+3. **Race condition**: What happens if --touch and --can-edit race on the task's timestamp?
+
+## Findings
+- The activity clock uses filesystem mtime, which IS manipulable by `touch` — but this is by design (the `--touch` command is the official way to reset)
+- The 30-minute threshold gives reasonable headroom for long-running work
+- Race conditions are minimal since status.py uses atomic file operations
+
+## Verdict
+No exploitable vulnerabilities found.