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/harden-dashboard-security/SPEC.md

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+# Harden Dashboard Security
+
+## Goal
+
+Close the security gaps identified by the adversarial audit: missing CORS headers, filesystem-sourced task names that bypass validation, and unbounded content-length handling on POST.
+
+## Requirements
+
+### R1. Add CORS headers
+
+The dashboard serves no CORS headers. When bound to `0.0.0.0` (documented in `__main__.py`), any webpage can call the API — including approving/rejecting tasks via POST.
+
+**Fix**: In `DashboardHandler._send_json()` and `_send_error()`, add:
+- `Access-Control-Allow-Origin: *` (or configurable via `--cors-origin`)
+- `Access-Control-Allow-Methods: GET, POST, OPTIONS`
+- `Access-Control-Allow-Headers: Content-Type`
+- Handle `OPTIONS` preflight requests for the review endpoint
+
+### R2. Validate filesystem-sourced task names
+
+`discover_tasks()` at `task.py:248` reads directory names directly from `iterdir()`. The `_validate_task_name` regex only applies to API path parsing. A task directory created via `mkdir` with special characters (e.g., quotes, HTML) will be served to the JS client, which injects names into `onclick` attributes and `innerHTML`.
+
+**Fix**: In `discover_tasks()`, skip directories whose names contain characters outside `[A-Za-z0-9_-]`. Log a warning for invalid names.
+
+### R3. Add content-length bound check on POST regardless of R2 from wire-dashboard-config
+
+Even if the caching task isn't done yet, add a quick defensive check:
+- If `Content-Length` header > `MAX_POST_BODY`, return 413
+- If `Content-Length` header is missing or <= 0, return 400
+
+### R4. Escape task names in JS HTML injection points
+
+In `dashboard.js:renderDetail()`, `renderTaskCard()`, and `renderTimeline()`, task names are interpolated into HTML. While R2 prevents most dangerous names, defense in depth requires:
+
+- Use `escapeHtml()` on `task.display_name` before injection
+- Use `data-*` attributes instead of `onclick` for review buttons (pass task name via `dataset`)
+
+### R5. Add `X-Content-Type-Options: nosniff` header
+
+All responses should include `X-Content-Type-Options: nosniff` to prevent MIME type sniffing.
+
+## Acceptance Criteria
+
+- [ ] All API responses include `Access-Control-Allow-Origin` header
+- [ ] `OPTIONS /api/task/{name}/review` returns 200 with appropriate CORS headers
+- [ ] Task directory named `task-with'quote` is excluded from `discover_tasks()` output
+- [ ] Task directory named `valid-task-123` is included
+- [ ] POST with `Content-Length: 1000000` returns 413 regardless of caching task status
+- [ ] `escapeHtml()` applied to `display_name` in all JS interpolation points
+- [ ] Review buttons use `data-task` attribute instead of inline `onclick`
+- [ ] All responses include `X-Content-Type-Options: nosniff`
+
+## Non-Goals
+
+- Not adding authentication (the dashboard is a local single-user tool)
+- Not adding HTTPS (out of scope for a dev tool)
+- Not rate-limiting (single-user, single-threaded server)