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/task-detail-modal/BUG_REPORT.md

@@ -1,18 +0,0 @@
-# Bug Report: Centered Modal for Task Detail
-
-## Methodology
-Reviewed dashboard.js, styles.css, index.html for modal behavior.
-
-## Acceptance Criteria
-| # | Criterion | Result |
-|---|-----------|--------|
-| 1 | Centered with 720px max-width, 85vh max-height | ✅ |
-| 2 | Content scrollable | ✅ |
-| 3 | Backdrop click closes | ✅ |
-| 4 | Escape key closes | ✅ |
-| 5 | Existing functionality preserved | ✅ |
-
-## Findings
-None.
-
-## Verdict: PASS