fix(regression): use custom-html-bkp-bad recipe for bad-backup canary

backupbot-two ignores nonexistent backup paths and backs up the whole
volume, making the bad-path approach unreliable. New approach:
- Create recipe-maintainers/custom-html-bkp-bad on Gitea (custom-html
  without backupbot.backup=true label) — SHA 4e584063a99a
- Add tests/custom-html-bkp-bad/recipe_meta.py with BACKUP_CAPABLE=True
  so the harness runs the backup tier despite auto-detect returning False
- Without a labeled container, backup-bot-two produces no snapshot →
  parse_snapshot_id=None → test_backup_artifact fails → backup=RED ✓

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

tests/custom-html-bkp-bad/recipe_meta.py

@@ -0,0 +1,5 @@
+# custom-html-bkp-bad — regression fixture for bad-backup canary.
+# This recipe is custom-html WITHOUT backupbot labels. Setting BACKUP_CAPABLE=True here forces the
+# harness to run the backup tier; the recipe itself has no backupbot service, so
+# `abra app backup create` produces no snapshot → test_backup_artifact fails → backup tier RED.
+BACKUP_CAPABLE = True

tests/regression/test_canaries.py

@@ -124,11 +124,13 @@ _BAD_UPGRADE = {
 
 _BAD_BACKUP = {
     "id": "bad-backup",
-    "recipe": "custom-html",
-    "src": "recipe-maintainers/custom-html",
-    # Pin: regression-bad-backup @ 2026-06-02 — backupbot.backup.path=/nonexistent-path-cc-ci-canary-bad
-    # `abra app backup create` fails → backup tier RED. install+upgrade still PASS.
-    "ref": "cd52b3a02d2cc1a73ec598766cc1bf1c62b465ec",
+    "recipe": "custom-html-bkp-bad",
+    "src": "recipe-maintainers/custom-html-bkp-bad",
+    # Pin: custom-html-bkp-bad main @ 2026-06-02 — custom-html WITHOUT backupbot labels.
+    # cc-ci recipe_meta sets BACKUP_CAPABLE=True → harness runs backup tier.
+    # No backupbot.backup=true label → backup-bot-two finds no containers → no snapshot.
+    # parse_snapshot_id returns None → test_backup_artifact fails → backup tier RED.
+    "ref": "4e584063a99aa9f4d05fe1b54a7e4d54356b524f",
     "expected_green": False,
     "stages": "install,upgrade,backup",
     "failing_tier": "backup",