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/start_watch_mode.md

@@ -1,3 +1,11 @@
+---
+method: POST
+path: /api/scanner/watch/start
+auth: jwt+admin
+area: scanner
+---
+<!-- source: internal/handlers/scanner.go:314 Handler.StartWatchMode -->
+
 # Start Watch Mode
 
 Start watch mode for a library to automatically detect and process new/modified files. Supports ebook, manga, and comic libraries with real-time file system monitoring.
@@ -24,7 +32,7 @@ Watch mode automatically detects and processes:
 
 ### Example Request
 
-```json
+```json example-request
 {
   "library_id": "550e8400-e29b-41d4-a716-446655440000"
 }
@@ -32,11 +40,10 @@ Watch mode automatically detects and processes:
 
 ## Response (200 OK)
 
-```json
+```json example-response
 {
   "message": "Watch mode started successfully",
-  "library_id": "uuid",
-  "status": "watching"
+  "library_id": "uuid"
 }
 ```