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/fix-dashboard-cors-origin/ADVERSARIAL_BUG_REPORT.md

@@ -1,12 +0,0 @@
-# Adversarial Bug Report: fix-dashboard-cors-origin
-
-## Attack Vectors Tested
-1. **Preflight OPTIONS request**: `do_OPTIONS()` returns 204 without CORS headers — browser will block cross-origin requests correctly
-2. **Missing security headers on error responses**: `_send_error()` uses `SECURITY_HEADERS` — verified
-3. **X-Frame-Options bypass**: `DENY` is the most restrictive value — no bypass
-4. **MIME type confusion**: `X-Content-Type-Options: nosniff` prevents browsers from sniffing content type
-
-## Findings
-No bugs found. The security headers are correctly applied to all response types.
-
-## Verdict: PASS