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/fix-guard-plugin-derailment/SPEC.md

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+# Fix Guard Plugin Derailment
+
+## Problem
+The automaton-guard plugin (`plugins/automaton-guard/plugin.ts:61-64`) calls `client.chat()` with `role: "user"` when an edit is blocked. This injects synthetic user messages that can derail agent context mid-operation.
+
+## Fix
+Replace the `client.chat()` call with returning an error through the output mechanism, using `throw new Error()` or equivalent so the harness handles the rejection cleanly without contaminating the agent's message history.
+
+## Verification
+- Guard plugin rejects blocked edits without injecting user messages
+- Agent context is not contaminated