docs(scanner): Beam batch 7 — all 10 scanner endpoints backfilled

Scanner surface frontmatter'd (scan/start/stop/cancel/status/active/
active-summary + watch start/stop/status) with provenance comments;
active-summary on a non-admin group.

Claude registry: 10 entries. Fixed handler drift Beam missed: scan_library
request has no "recursive"; scanner/start binds folder_paths (not
invented interval_seconds); scanner/stop binds no body; response is
{message, job_id, status} with 409 coalescing variant
{error, active_job_id}.

Gate fix in drift_test seed: registerScannerRoutes group seeds used bare
"jwt"/"admin" tokens invisible to authLabel; and silently passed before
only because the seeded set was unchecked. Seeds now 'jwtMiddleware'/
'AdminMiddleware' markers. Also: cleanup of a stale-merge-script residue
in collections/update_rule.md example (extra null keys). make test 9/9.

docs/developer/api/scanner/get_watch_mode_status.md

@@ -1,3 +1,11 @@
+---
+method: GET
+path: /api/scanner/watch/status
+auth: jwt+admin
+area: scanner
+---
+<!-- source: internal/handlers/scanner.go:376 Handler.GetWatchModeStatus -->
+
 # Get Watch Mode Status
 
 Get the watch mode status for a library.
@@ -26,18 +34,10 @@ Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
 
 ## Response (200 OK)
 
-```json
+```json example-response
 {
-  "library_id": "uuid",
-  "status": "watching",
-  "started_at": "2026-02-08T10:00:00Z",
-  "watched_folders": ["/path/to/library/folder1", "/path/to/library/folder2"],
-  "stats": {
-    "files_detected": 15,
-    "files_processed": 12,
-    "files_failed": 1,
-    "last_activity": "2026-02-08T11:30:00Z"
-  }
+  "total_watching": null,
+  "watching_libraries": null
 }
 ```