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/changelog/SPEC.md

@@ -0,0 +1,33 @@
+# SPEC: Changelog and Release Notes Process
+
+## Overview
+
+There's no changelog or release note process. Completed tasks produce a VERDICT.md but there's no aggregate record of what changed. This makes it hard to generate release notes or see the project's history at a glance.
+
+## Changes
+
+### 1. `CHANGELOG.md` at `~/.automaton/`
+
+Root-level changelog file with entries appended on task completion:
+
+```markdown
+# Changelog
+
+## [unreleased]
+
+### Added
+- description (#task-name)
+
+### Fixed
+- description (#task-name)
+```
+
+### 2. Update `.rules.md`
+
+Add a rule: "When a task reaches Resolution (VERDICT.md written), append an entry to CHANGELOG.md."
+
+## Acceptance Criteria
+
+- [ ] `~/.automaton/CHANGELOG.md` exists with [unreleased] header
+- [ ] `.rules.md` mentions changelog updates as part of task completion
+- [ ] Format is clean enough to use as release notes source