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/task-detail-modal/IMPLEMENTATION.md

@@ -0,0 +1,28 @@
+# Implementation: Centered Modal for Task Detail
+
+## Summary
+
+Replaced the narrow sliding side panel with a centered modal overlay for viewing task details.
+
+## Changes Made
+
+### `index.html`
+- Replaced `.detail-panel` fixed sidebar with `.modal-overlay` + `.modal-panel` container
+- Added `#btn-close-detail` button and backdrop click handler
+
+### `dashboard.js`
+- Updated all JS references from `detail-panel` to `detail-overlay`
+- `closeDetail()` hides overlay instead of sliding panel
+- Escape key handler added for modal close
+- Backdrop click closes modal
+
+### `styles.css`
+- `.modal-overlay` — fixed fullscreen backdrop with blur
+- `.modal-panel` — centered container, 720px max-width, 85vh max-height
+- Removed `.detail-panel` fixed positioning styles
+- Scrollable content within modal
+
+## Files Modified
+- `automaton/dashboard/html/index.html` — modal overlay structure
+- `automaton/dashboard/html/dashboard.js` — modal open/close logic
+- `automaton/dashboard/html/styles.css` — modal styling