Add -X delete operation, demo tape tests, and consolidate demos

- Add -X <id|name> to stop, disable, and remove a job's unit files;
  mutually exclusive with all other management options; 13 new tests
- Add demo/test-tapes.sh to verify all VHS tape commands run cleanly;
  wired into pre-commit hook alongside test.sh (combined badge count)
- Rename demo job names to *_home variants to avoid clashing with real
  user jobs; add per-tape preflight cleanup via -X
- Consolidate four demo GIFs into quickstart + all-features + editmode
  screenshot; remove notifications/services tapes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

badges/tests.json

@@ -1,6 +1,6 @@
 {
   "schemaVersion": 1,
   "label": "tests",
-  "message": "88 passed",
+  "message": "127 passed",
   "color": "brightgreen"
 }