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/register_device.md

@@ -1,3 +1,11 @@
+---
+method: POST
+path: /api/devices/register
+auth: none
+area: devices
+---
+<!-- source: internal/handlers/devices.go:123 DeviceHandler.InitiateRegistration -->
+
 # Register Device
 
 Register a new device for sync.
@@ -16,7 +24,7 @@ Register a new device for sync.
 
 ### Example Request
 
-```json
+```json example-request
 {
   "device_name": "My Kobo Clara",
   "device_type": "kobo",
@@ -26,8 +34,9 @@ Register a new device for sync.
 
 ## Response (201 Created)
 
-```json
+```json example-response
 {
+  "device_id": "550e8400-e29b-41d4-a716-446655440000",
   "registration_id": "registration-uuid",
   "auth_url": "https://bookhoard.com/devices/approve/abc123",
   "qr_code": "data:image/png;base64,iVBORw0KG...",