docs(auth,devices): Beam WO5 batch 3 — 15 endpoints backfilled, registry pinned

Beam backfilled auth core (login/register/refresh/logout/profile) and devices
core (list/update/delete/shelf CRUD/sidecar/register flow) with frontmatter,
provenance, and labeled examples. All claimed shapes verified against
handlers: AuthResponse {access_token, refresh_token omitempty, token_type,
expires_in, user}, update device {device_updated, device}, shelf wrappers,
DeviceAuthStatusResponse.

Claude registry verification: 15 entries pinned by type (LoginRequest,
RegisterRequest, AuthResponse, RefreshTokenRequest/Response, UserProfile,
DeviceListResponse, DeviceUpdateRequest, AddToShelfRequest, SidecarConfig,
DeviceRegistrationRequest/Response, DeviceAuthStatusRequest/Response).
Removed revoke_device.md — name-only duplicate of delete_device.md (same
DELETE /api/devices/:id route; was the last audit-orphan doc).

Gate catches this round (subtle Go serialization facts, now pinned in docs):
- uuid.UUID arrays never serialize as omitted: register/status response
  ALWAYS carries device_id (all-zeros while pending) despite omitempty
- update device request binds device_name, not name
- register response includes device_id alongside registration_id
- list devices response is a {devices, total} wrapper

docs/developer/api/devices/add_to_shelf.md

@@ -1,3 +1,11 @@
+---
+method: POST
+path: /api/devices/:id/shelves
+auth: jwt
+area: devices
+---
+<!-- source: internal/handlers/media.go:256 MediaHandler.AddToShelf -->
+
 # Add to Shelf
 
 Add a media item to a device's shelf (Kobo reading shelf).
@@ -14,25 +22,30 @@ Add a media item to a device's shelf (Kobo reading shelf).
 
 ## Request Body
 
-| Field         | Type          | Required | Description                     |
-| ------------- | ------------- | -------- | ------------------------------- |
-| media_item_id | string (UUID) | Yes      | Media item UUID to add to shelf |
+| Field          | Type            | Required | Description                     |
+| -------------- | --------------- | -------- | ------------------------------- |
+| media_item_ids | array of string | Yes      | Media item UUIDs to add to shelf |
+| shelf_name     | string          | No       | Shelf name (default "Default")  |
+| shelf_position | int             | No       | Starting shelf position         |
 
 ### Example Request
 
-```json
+```json example-request
 {
-  "media_item_id": "550e8400-e29b-41d4-a716-446655440001"
+  "media_item_ids": ["550e8400-e29b-41d4-a716-446655440001"],
+  "shelf_name": "Default",
+  "shelf_position": 0
 }
 ```
 
-## Response (201 Created)
+## Response (200 OK)
 
-```json
+```json example-response
 {
-  "message": "Item added to shelf successfully",
-  "device_id": "uuid",
-  "media_item_id": "uuid"
+  "status": "success",
+  "added_count": 1,
+  "shelf_name": "Default",
+  "total_count": 1
 }
 ```