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-dead-end-phases/IMPLEMENTATION.md

@@ -1,10 +0,0 @@
-# IMPLEMENTATION.md — Fix Dead-End Phases
-
-## Changes Made
-- `scripts/status.py:91`: Changed `"decomposition:approved": []` to `"decomposition:approved": ["complete"]`
-- `scripts/status.py:103`: Added `"human_intervention": ["referee", "complete"]` to LEGAL_TRANSITIONS
-
-## How It Works
-- Parent tasks at decomposition:approved can now transition to complete (after sub-tasks finish)
-- Human intervention tasks can transition back to referee or to complete
-- Verified both transitions are legal via status.py --transition