docs(ui): cookie-rendered sidebar state, data-collapsed CSS, working overview links + link-checker gate

Three problems, one root cause each:

1. Sidebar jump: the server rendered its own default (current section
   open, rest collapsed) and restoreDocsNav corrected it after paint —
   open-then-close. Fix: persistence moved server-side. toggleCollapsible
   now writes a docs_nav cookie (strictly-necessary UI state, no
   identifiers, SameSite=Lax); ApplyNavOverrides merges it into the nav
   before render, so first paint IS the visitor's state. The post-paint
   restore is deleted.

2. Arrows out of sync / double-click: two visibility mechanisms
   disagreed. There was NO data-collapsed CSS at all — collapsed sections
   were only ever hidden by JS after paint, and the arrow rotation came
   from a different (server) state. Now: style.css hides on
   [data-collapsed=true] (single source of truth, server-rendered),
   applyCollapsed sets only the attribute, arrows rotate from the same
   merged value. Live check: 37/37 collapsibles arrow-consistent.

3. api-reference.md links: all 20+ quick links were directory-style
   (authentication/ etc.) that 404 on the docs site, plus stale targets
   (books/, ../collections-api.md, websocket 'coming soon'). Rewritten to
   real per-file links — all 9 unique targets return 200 live. Same rot
   fixed in admin/hash-conflicts.md, development.md, android-app.md,
   create_media_item.md, koreader-protocol.md; docs/index.md redirected
   from the deleted collections-api monolith (stale 530-line duplicate of
   the gated api/collections docs — deleted, per the WO2 doctrine).

New gate: TestDocsRelativeLinks walks docs/developer/** and fails make
test on any relative link that is directory-style or unresolvable —
overview links can never silently rot again.

docs/developer/api/admin/hash-conflicts.md

@@ -107,5 +107,5 @@ Files on disk are never deleted — resolution only affects database rows.
 
 ## Related Endpoints
 
-- [System Settings API](../system/settings.md) — scanning configuration
-- [Scanner API](../scanner/) — triggering scans and watch mode
+- [System Settings API](../system/get_settings.md) — scanning configuration
+- [Scanner API](../scanner/scan_library.md) — triggering scans and watch mode

docs/developer/api/api-reference.md

@@ -4,34 +4,33 @@ Complete reference for Bookhoard REST API endpoints.
 
 ## Quick Links
 
-- [Authentication](authentication/) - User registration, login, tokens
-- [Users](users/) - Profile management
-- [Admin](admin/) - Admin operations (user management)
-- [Libraries](libraries/) - Library management
-- [Books](books/) - Bulk book operations and downloads
-- [Media Items](media-items/) - Media item operations
-- [Progress](progress/) - Reading progress tracking
-- [Notes](notes/) - User notes management
-- [Highlights](highlights/) - Book highlights
-- [Ratings](ratings/) - Book ratings
-- [Devices](devices/) - Device registration, sync, and shelf management
-- [Analytics](analytics/) - Usage statistics
-- [Book Matching](book-matching/) - Search and link books
-- [Collections](collections/) - See [Collections API](../collections-api.md)
-- [Conflicts](conflicts/) - Sync conflict resolution
-- [Queue](queue/) - Sync queue management
-- [Scanner](scanner/) - Library scanning and watch mode (admin)
-- [System](system/) - Tunable system settings and configuration (admin)
-- [OPDS](opds/) - Open Publication Distribution
-- [KOReader](koreader/) - KOReader sync protocol
-- [Kobo](kobo/) - Kobo sync protocol (coming soon)
-- [WebSocket](websocket/) - Real-time sync events
+- [Authentication](authentication/login.md) - User registration, login, tokens
+- [Users](users/get_profile.md) - Profile management
+- [Admin](admin/list_users.md) - Admin operations (user management)
+- [Libraries](libraries/list_libraries.md) - Library management
+- [Media Items](media-items/get_media_item.md) - Media item operations
+- [Progress](progress/get_media_progress.md) - Reading progress tracking
+- [Notes](notes/get_notes.md) - User notes management
+- [Highlights](highlights/get_highlights.md) - Book highlights
+- [Ratings](ratings/get_ratings.md) - Book ratings
+- [Devices](devices/get_devices.md) - Device registration, sync, and shelf management
+- [Analytics](analytics/get_analytics.md) - Usage statistics
+- [Book Matching](book-matching/search_books.md) - Search and link books
+See [Collections Endpoints](collections/list_collections.md)
+- [Conflicts](conflicts/list_conflicts.md) - Sync conflict resolution
+- [Queue](queue/list_all_queue_items.md) - Sync queue management
+- [Scanner](scanner/scan_library.md) - Library scanning and watch mode (admin)
+- [System](system/get_settings.md) - Tunable system settings and configuration (admin)
+- [OPDS](opds/feeds.md) - Open Publication Distribution
+- [KOReader](koreader/sync_progress.md) - KOReader sync protocol
+- [Kobo](kobo/initialization.md) - Kobo sync protocol (coming soon)
+- [WebSocket](websocket/protocol.md) - Real-time sync events
 
 ---
 
 ## Authentication
 
-See [Authentication Endpoints](authentication/)
+See [Authentication Endpoints](authentication/login.md)
 
 - POST /api/auth/register - Register new user
 - POST /api/auth/login - User login
@@ -48,7 +47,7 @@ See [Authentication Endpoints](authentication/)
 
 ## Admin
 
-See [Admin Operations](admin/)
+See [Admin Operations](admin/list_users.md)
 
 - GET /api/auth/users - List all users (admin)
 - PUT /api/auth/users/:id/max-devices - Update user device limit (admin)
@@ -57,11 +56,11 @@ See [Admin Operations](admin/)
 
 ## Users & Profiles
 
-See [User Management](users/)
+See [User Management](users/get_profile.md)
 
 ## Libraries
 
-See [Library Management](libraries/)
+See [Library Management](libraries/list_libraries.md)
 
 - GET /api/libraries/types - Get library types
 - POST /api/libraries - Create library (admin)
@@ -83,13 +82,13 @@ See [Library Management](libraries/)
 
 ## Media Items
 
-See [Media Item Operations](media-items/)
+See [Media Item Operations](media-items/get_media_item.md)
 
 - GET /api/media-items - List media items
 - GET /api/media-items/:id - Get media item details
 - POST /api/media-items/bulk-delete - Bulk delete media items
 - POST /api/media-items/bulk-update - Bulk update media items (tags/contributors with normalization)
-- GET /uploads/library-{library_id}/{file_path} - Download book file / cover (JWT; see [Download Media Item](media-items/download_media_item.md))
+- GET /uploads/library-{library_id}/{file_path} - Download book file / cover (JWT; see [Download Media Item](media-items/download_media_item_file.md))
 - POST /api/media-items/:id/rating - Create rating
 - GET /api/media-items/:id/rating - Get rating
 - PUT /api/media-items/:id/rating - Update rating
@@ -117,7 +116,7 @@ See [Media Item Operations](media-items/)
 
 ## Reading Progress
 
-See [Progress Tracking](progress/) — in particular the
+See [Progress Tracking](progress/get_media_progress.md) — in particular the
 [Position Contract](progress/position-contract.md) (verification,
 healing, the OPF spine numbering hazard, and offset currencies) before
 writing a client.
@@ -129,15 +128,15 @@ writing a client.
 
 ## Notes & Highlights
 
-See [Notes Management](notes/) and [Highlights Management](highlights/)
+See [Notes Management](notes/get_notes.md) and [Highlights Management](highlights/get_highlights.md)
 
 ## Ratings
 
-See [Ratings System](ratings/)
+See [Ratings System](ratings/get_ratings.md)
 
 ## Device Management
 
-See [Device Registration & Sync](devices/)
+See [Device Registration & Sync](devices/get_devices.md)
 
 - POST /api/devices/register - Initiate device registration
 - POST /api/devices/register/status - Check registration status
@@ -157,7 +156,7 @@ See [Device Registration & Sync](devices/)
 
 ## System Settings & Configuration
 
-See [System API](system/)
+See [System API](system/get_settings.md)
 
 - GET /api/system/settings - List all tunable settings with metadata (admin)
 - PUT /api/system/settings - Validate, persist, and reload a single setting (admin)
@@ -166,7 +165,7 @@ See [System API](system/)
 
 ## Analytics
 
-See [Usage Analytics](analytics/)
+See [Usage Analytics](analytics/get_analytics.md)
 
 - GET /api/analytics/reading-stats - Get reading statistics
 - GET /api/analytics/device-usage - Get device usage stats
@@ -174,7 +173,7 @@ See [Usage Analytics](analytics/)
 
 ## Book Matching & Linking
 
-See [Book Matching](book-matching/)
+See [Book Matching](book-matching/search_books.md)
 
 - GET /api/media-items/search - Search media items
 - POST /api/sync/books/query - Query books for matching
@@ -191,11 +190,11 @@ See [Book Matching](book-matching/)
 
 ## Collections
 
-See [Collections API](../collections-api.md) or [Collections Endpoints](collections/)
+See [Collections Endpoints](collections/list_collections.md)
 
 ## Conflicts
 
-See [Conflict Resolution](conflicts/)
+See [Conflict Resolution](conflicts/list_conflicts.md)
 
 - GET /api/conflicts - List conflicts
 - GET /api/conflicts/:id - Get conflict details
@@ -207,7 +206,7 @@ See [Conflict Resolution](conflicts/)
 
 ## Queue Management
 
-See [Sync Queue](queue/)
+See [Sync Queue](queue/list_all_queue_items.md)
 
 - GET /api/queue/devices/:device_id/stats - Get device queue stats
 - GET /api/queue/devices/:device_id/items - List device queue items
@@ -218,7 +217,7 @@ See [Sync Queue](queue/)
 
 ## Scanner (Admin)
 
-See [Scanner Operations](scanner/)
+See [Scanner Operations](scanner/scan_library.md)
 
 - [Scanner Overview](scanner/overview.md) - Supported formats, metadata extraction, and features
 - POST /api/scanner/scan - Scan library (one-time) (ebooks, manga, comics)
@@ -231,7 +230,7 @@ See [Scanner Operations](scanner/)
 
 ## OPDS
 
-See [OPDS Feeds](opds/)
+See [OPDS Feeds](opds/feeds.md)
 
 - GET /opds/devices/:deviceId/catalog - Get device catalog
 - GET /opds/devices/:deviceId/search - Search device catalog
@@ -242,7 +241,7 @@ See [OPDS Feeds](opds/)
 
 ## KOReader Sync Protocol
 
-See [KOReader Sync](koreader/) and [Sync Protocol](sync/koreader-protocol.md)
+See [KOReader Sync](koreader/sync_progress.md) and [Sync Protocol](sync/koreader-protocol.md)
 
 - POST /api/sync/koreader/progress - Sync reading progress
 - GET /api/sync/koreader/resolve?sha256={hash} - Resolve a book UUID by file SHA-256
@@ -254,7 +253,7 @@ See [KOReader Sync](koreader/) and [Sync Protocol](sync/koreader-protocol.md)
 
 > **Status: Coming Soon** — Native Kobo sync is implemented server-side but not yet supported on real devices. These endpoints are under active development and may change.
 
-See [Kobo Sync](kobo/) and [Sync Protocol](sync/kobo-protocol.md)
+See [Kobo Sync](kobo/initialization.md) and [Sync Protocol](sync/kobo-protocol.md)
 
 - POST /api/sync/kobo/:token/markup - Sync markup highlights
 - POST /api/sync/kobo/:token/bookmark - Sync bookmarks
@@ -264,7 +263,7 @@ See [Kobo Sync](kobo/) and [Sync Protocol](sync/kobo-protocol.md)
 
 ## WebSocket
 
-See [WebSocket API](websocket/)
+See [WebSocket API](websocket/protocol.md)
 
 - WS /ws/sync - Real-time sync events and notifications
 

docs/developer/api/collections/collections-api.md

@@ -1,35 +0,0 @@
-# Collections API
-
-See [Collections API](../../collections-api.md) for complete collections documentation.
-
-## Quick Links
-
-- [List Collections](list_collections.md) - Get all collections
-- [Get Collection](get_collection.md) - Get collection details
-- [Create Collection](create_collection.md) - Create a new collection
-- [Update Collection](update_collection.md) - Update collection metadata
-- [Delete Collection](delete_collection.md) - Delete a collection
-- [Add Auto-Assign Rule](add_auto_assign_rule.md) - Add automatic book assignment rule
-- [Remove Auto-Assign Rule](remove_auto_assign_rule.md) - Remove assignment rule
-- [Test Rule](test_rule.md) - Test assignment rule
-- [Bulk Assign](bulk_assign.md) - Bulk assign books to collection
-- [Create Shelf Mapping](create_shelf_mapping.md) - Map collection to device shelf
-- [Delete Shelf Mapping](delete_shelf_mapping.md) - Remove shelf mapping
-
----
-
-## Overview
-
-Collections allow you to organize your books into custom groups with automatic assignment rules.
-
-## Features
-
-- **Manual Assignment**: Add specific books to collections
-- **Auto-Assignment**: Define rules to automatically assign books based on metadata
-- **Device Sync**: Collections sync as shelves on Kobo/KOReader devices
-- **Flexible Rules**: Filter by genre, series, tags, and more
-
-## See Also
-
-- [Collections API](../../collections-api.md) - Complete API reference
-- [Sync Guide](../../user/sync-guide.md) - How collections sync to devices

docs/developer/api/media-items/create_media_item.md

@@ -22,7 +22,7 @@ Create a new media item (Admin only).
 2. Add folder(s) to the library: `POST /api/libraries/{library_id}/folders`
 3. Then create media items: `POST /api/media-items`
 
-See [Library API documentation](../libraries/) for more details.
+See [Library API documentation](../libraries/list_libraries.md) for more details.
 
 ## Request Body
 

docs/developer/api/sync/koreader-protocol.md

@@ -202,7 +202,7 @@ as a server annotation deletion.
 
 Every client/sync interface (KOReader, Kobo, OPDS, the device-link UI, and any
 future mobile app) resolves books through a single shared service:
-[`internal/services/book_resolver.go`](../../../internal/services/book_resolver.go).
+`internal/services/book_resolver.go` (in the repository source).
 The import-time SHA-256 (stored on `media_items.file_sha256`, plus a per-format
 hash on `media_item_formats.file_sha256` for KEPUB/PDF) is the canonical shared
 identifier. New clients should resolve by SHA-256 via `BookResolver` rather than