docs(quick-3): complete playlist multi-select plan

- Add 3-SUMMARY.md with execution results
- Update STATE.md with quick task 003 entry

.planning/STATE.md

@@ -79,6 +79,7 @@ None currently.
 |---|-------------|------|--------|-----------|
 | 001 | Multi-playlist import support | 2026-02-28 | 50c8a33 | [001-multi-playlist-import-support](./quick/001-multi-playlist-import-support/) |
 | 002 | Auto-rename duplicate playlists on import | 2026-02-28 | 8ba8bbe | [002-auto-rename-duplicate-playlists-on-import](./quick/002-auto-rename-duplicate-playlists-on-import/) |
+| 003 | Add multi-select to playlist view with batch delete | 2026-02-28 | c92ced2 | [3-add-multi-select-to-playlist-view-with-c](./quick/3-add-multi-select-to-playlist-view-with-c/) |
 
 ## Session Continuity
 
@@ -98,5 +99,5 @@ None currently.
 
 ---
 *State initialized: 2026-02-27*
-Last activity: 2026-02-28 - Completed quick task 002: Auto-rename duplicate playlists on import
+Last activity: 2026-02-28 - Completed quick task 003: Add multi-select to playlist view with batch delete
 *Last updated: 2026-02-28*

.planning/quick/3-add-multi-select-to-playlist-view-with-c/3-SUMMARY.md

@@ -0,0 +1,66 @@
+---
+phase: quick
+plan: 3
+subsystem: frontend/playlist-view
+tags: [multi-select, batch-delete, UX, playlist]
+dependency_graph:
+  requires: []
+  provides: [playlist-multi-select, playlist-batch-delete]
+  affects: [playlist-view]
+tech_stack:
+  added: []
+  patterns: [Set-based-selection, modifier-key-handling]
+key_files:
+  modified:
+    - frontend/src/components/playlist-view/playlist-view.ts
+decisions:
+  - Used simple Set<number> for playlist selection (matching cover-grid pattern) instead of a second SelectionController — playlists are index-based and few in number
+  - Playlist-level and track-level selections are mutually exclusive to prevent confusing UX
+metrics:
+  duration: 2 min
+  completed: "2026-02-28T19:15:35Z"
+---
+
+# Quick Task 3: Add Multi-Select to Playlist View with Batch Delete Summary
+
+**One-liner:** Playlist-level Ctrl+Click/Shift+Click multi-select with adaptive context menu and batch delete
+
+## What Was Done
+
+### Task 1: Add playlist-level multi-select state and selection handling
+**Commit:** `e13151f`
+
+- Added `selectedPlaylists: Set<number>` state and `lastSelectedPlaylistIndex` anchor for range selection
+- Replaced `handleToggle` with `handlePlaylistHeaderClick` that handles three modes:
+  - **Ctrl/Cmd+Click:** Toggle individual playlist in/out of selection
+  - **Shift+Click:** Range-select from anchor to clicked playlist (inclusive)
+  - **Plain click:** Clear selection and expand/collapse as before
+- Added mutual exclusion: entering track selection scope (`ensureSelectionScope`) clears playlist selection
+- Added `.playlist-header.selected` CSS class with blue highlight (`--yj-selection-bg`)
+- Updated `clearSelectionHandler` to also clear playlist selection on outside clicks
+- Wired header `@click` to new handler and added `selected` class binding in template
+
+### Task 2: Wire playlist context menu to support batch delete
+**Commit:** `c92ced2`
+
+- Updated `handlePlaylistContextMenu` to respect existing multi-selection: if right-clicked playlist is already selected, preserve the selection; otherwise replace with single selection
+- Made `onPlaylistContextAction` async to support awaiting batch delete operations
+- Added batch delete: when `selectedPlaylists.size > 1`, iterates all selected playlist IDs calling `DeletePlaylist` for each, then refreshes once
+- Context menu adapts based on selection count:
+  - **Multi-select (>1):** Shows "Delete N Playlists" only (rename hidden)
+  - **Single (<=1):** Shows "Rename" + "Delete Playlist" as before
+- Clears playlist selection after any context action completes
+
+## Deviations from Plan
+
+None — plan executed exactly as written.
+
+## Verification
+
+- TypeScript compilation passes with zero errors (`npx tsc --noEmit`)
+- Pre-commit hooks (frontend-typecheck) pass on both commits
+
+## Self-Check: PASSED
+
+- All modified files exist on disk
+- Both task commits verified in git history (e13151f, c92ced2)