docs(quick-8): complete duplicate tracks dialog plan

- Add 8-SUMMARY.md with execution results
- Update STATE.md with quick task 008 entry

.planning/STATE.md

@@ -84,14 +84,15 @@ None currently.
 | 005 | Add sort dropdown to playlist view | 2026-03-01 | 5c07485 | [5-add-sort-dropdown-to-playlist-view](./quick/5-add-sort-dropdown-to-playlist-view/) |
 | 006 | Remove list icon from playlist names, add favorites icon to default | 2026-03-01 | 3c19766 | [6-remove-list-icon-from-playlist-names-and](./quick/6-remove-list-icon-from-playlist-names-and/) |
 | 007 | Pin default playlist to top of playlist view | 2026-03-01 | e6378e1 | [7-pin-default-playlist-to-top-of-playlist-](./quick/7-pin-default-playlist-to-top-of-playlist-/) |
+| 008 | Add duplicate tracks dialog to playlist | 2026-03-01 | 917a79a | [8-add-duplicate-tracks-dialog-to-playlist](./quick/8-add-duplicate-tracks-dialog-to-playlist/) |
 
 ## Session Continuity
 
 ### Last Session
 
 **Date:** 2026-03-01
-**What happened:** Executed quick task 007 — pin default playlist to top of playlist view with config toggle
+**What happened:** Executed quick task 008 — add duplicate tracks dialog to playlist additions
-**Where we stopped:** Completed quick task 007 (all tasks, verification passed)
+**Where we stopped:** Completed quick task 008 (all tasks, verification passed)
 **Next action:** `/gsd-plan-phase 2` to create execution plan for Backend Correctness
 
 ### Context for Next Session
@@ -103,8 +104,9 @@ None currently.
 - Quick task 005: Playlist view now has sort dropdown (Recent, Name, Date Created, Track Count) with persistent preferences
 - Quick task 006: Playlist list icon removed; default playlist shows favorites icon (heart/star per config), others show no icon
 - Quick task 007: Default playlist pinned to top of playlist list (configurable toggle in Settings > Favorites)
+- Quick task 008: Duplicate tracks dialog intercepts playlist additions — shows Add/Skip per duplicate with batch-apply toggle
 
 ---
 *State initialized: 2026-02-27*
-Last activity: 2026-03-01 - Completed quick task 007: Pin default playlist to top of playlist view
+Last activity: 2026-03-01 - Completed quick task 008: Add duplicate tracks dialog to playlist
 *Last updated: 2026-03-01*

.planning/quick/8-add-duplicate-tracks-dialog-to-playlist/8-SUMMARY.md

@@ -0,0 +1,83 @@
+---
+phase: quick
+plan: 8
+subsystem: playlist
+tags: [playlist, duplicate-detection, dialog, ux]
+dependency_graph:
+  requires: []
+  provides: [duplicate-track-detection, duplicate-tracks-dialog]
+  affects: [playlist-picker, playlist-view]
+tech_stack:
+  added: []
+  patterns: [wa-dialog, wa-switch, lit-component]
+key_files:
+  created:
+    - frontend/src/components/duplicate-tracks-dialog/duplicate-tracks-dialog.ts
+  modified:
+    - backend/playlist/playlist.go
+    - frontend/src/components/playlist-picker/playlist-picker.ts
+    - frontend/src/components/playlist-view/playlist-view.ts
+    - frontend/wailsjs/go/models.ts
+    - frontend/wailsjs/go/playlist/Service.d.ts
+    - frontend/wailsjs/go/playlist/Service.js
+decisions:
+  - Used DuplicateCheckResult wrapper struct for Wails (T, error) return signature compatibility
+  - Reused GetPlaylistTracksWithMetadata query for duplicate detection (avoids new SQL query)
+metrics:
+  duration: 12 min
+  completed: 2026-03-01
+  tasks: 3/3
+---
+
+# Quick Task 8: Add Duplicate Tracks Dialog to Playlist Summary
+
+Backend duplicate detection using existing playlist track queries, new Lit dialog component stepping through duplicates one-by-one with Add/Skip and batch-apply toggle, wired into both playlist-picker context menu and playlist-view drag-drop flows.
+
+## What Was Built
+
+### Backend: FindDuplicateTracksInPlaylist (Task 1)
+
+- Added `DuplicateTrackInfo` and `DuplicateCheckResult` types to `backend/playlist/playlist.go`
+- Implemented `FindDuplicateTracksInPlaylist(playlistID, filePaths)` method on `Service`
+- Uses existing `GetPlaylistTracksWithMetadata` query to build a map of existing file paths
+- Partitions incoming file paths into duplicates (with metadata) and unique paths
+- Wails TypeScript bindings regenerated with proper type mappings
+
+### Frontend: DuplicateTracksDialog Component (Task 2)
+
+- New `<duplicate-tracks-dialog>` Lit component at `frontend/src/components/duplicate-tracks-dialog/`
+- Follows existing wa-dialog patterns from `track-details.ts` and `phantom-resolver.ts`
+- Shows duplicate track count header, progress indicator (Track N of M)
+- Track card displays Title, Artist, Album, Duration for the current duplicate
+- "Add" button includes duplicate in final add; "Skip" excludes it
+- `wa-switch` toggle "Apply to all remaining" batch-applies the current choice
+- `finalize()` combines unique paths + user-approved duplicates, calls `AddTracksToPlaylist`, dispatches `playlist-action-complete`
+
+### Frontend: Integration (Task 3)
+
+- **playlist-picker.ts**: `handleSelectPlaylist` now calls `FindDuplicateTracksInPlaylist` before adding. If duplicates found, opens the dialog instead. Otherwise adds directly as before.
+- **playlist-view.ts**: `onPlaylistDrop` drag-drop handler similarly checks for duplicates before adding. Shows dialog when duplicates found.
+- Both components render `<duplicate-tracks-dialog>` and listen for `playlist-action-complete` to trigger refresh.
+
+## Commits
+
+| Task | Name | Commit | Key Files |
+|------|------|--------|-----------|
+| 1 | Add backend FindDuplicateTracksInPlaylist | `83de934` | backend/playlist/playlist.go, wailsjs bindings |
+| 2 | Create duplicate-tracks-dialog component | `9f3ba2b` | frontend/src/components/duplicate-tracks-dialog/duplicate-tracks-dialog.ts |
+| 3 | Wire duplicate detection into playlist-picker and playlist-view | `917a79a` | playlist-picker.ts, playlist-view.ts |
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Verification
+
+- [x] `go build ./...` — backend compiles
+- [x] `npx tsc --noEmit` — frontend typechecks
+- [x] Wails bindings regenerated with `FindDuplicateTracksInPlaylist`
+- [x] `DuplicateCheckResult` and `DuplicateTrackInfo` types in generated models.ts
+
+## Self-Check: PASSED
+
+All created files exist, all commits found, all modified files present.