docs(quick-18): complete multi-column metadata display plan

- Add 18-SUMMARY.md with execution results
- Update STATE.md quick tasks table

.planning/STATE.md

@@ -111,6 +111,7 @@ Decisions from v1.0 are archived in PROJECT.md Key Decisions table. Key patterns
 |---|-------------|------|--------|-----------|
 | 16 | add ctrl+a hotkey to multi-select views to select all items | 2026-03-07 | 043c74c | [16-add-ctrl-a-hotkey-to-multi-select-views-](./quick/16-add-ctrl-a-hotkey-to-multi-select-views-/) |
 | 17 | refactor playlist view to use subpages | 2026-03-08 | 955cd68 | [17-refactor-playlist-view-to-use-subpages-l](./quick/17-refactor-playlist-view-to-use-subpages-l/) |
+| 18 | add multi-column metadata display to playlist-details | 2026-03-08 | ce23177 | [18-add-multi-column-metadata-display-to-pla](./quick/18-add-multi-column-metadata-display-to-pla/) |
 
-Last activity: 2026-03-08 - Completed quick task 17: refactor playlist view to use subpages
+Last activity: 2026-03-08 - Completed quick task 18: add multi-column metadata display to playlist-details
 *Last updated: 2026-03-08*

.planning/quick/18-add-multi-column-metadata-display-to-pla/18-SUMMARY.md

@@ -0,0 +1,51 @@
+---
+phase: quick-18
+plan: 1
+subsystem: frontend/playlist-details
+tags: [ui, grid-layout, playlist]
+dependency_graph:
+  requires: [playlist.Track, formatMilliseconds]
+  provides: [multi-column-playlist-track-display]
+  affects: [playlist-details]
+tech_stack:
+  added: []
+  patterns: [css-grid-template-columns, tabular-nums, text-overflow-ellipsis]
+key_files:
+  modified:
+    - frontend/src/components/playlist-details/playlist-details.ts
+decisions: []
+metrics:
+  duration: 2 min
+  completed: "2026-03-08T13:36:12Z"
+---
+
+# Quick Task 18: Multi-Column Metadata Display in Playlist Details — Summary
+
+Replaced single-row `<track-info>` component rendering with a 5-column CSS grid layout (#, Title, Artist, Album, Duration) including a column header row, matching track-list's visual style.
+
+## Changes Made
+
+### Task 1: Replace track-info rendering with multi-column grid layout
+**Commit:** `ce23177`
+
+- Removed `<track-info>` component import (no longer used)
+- Added `formatMilliseconds` import from `@utils/time` for duration formatting
+- Added `.track-header` row with column labels: #, Title, Artist, Album, Duration
+- Replaced `<track-info>` element with inline `<span>` grid cells showing track metadata
+- Added 1-indexed playlist order number in `#` column (`trackIndex + 1`)
+- Phantom tracks span the full grid width via `grid-column: 1 / -1`
+- Added CSS grid styles: `grid-template-columns: 40px 1fr 1fr 1fr 80px`
+- Column-specific styles: center-aligned `#`, right-aligned duration, tabular-nums, text truncation with ellipsis
+- Removed stale `.track-item:last-child { border-bottom: none }` rule
+- Updated `.track-item` padding from `6px 0` to `6px 8px` for grid alignment
+
+## Deviations from Plan
+
+None — plan executed exactly as written.
+
+## Verification
+
+- `cd frontend && npx tsc --noEmit` — passed (0 errors)
+- Pre-commit hook `frontend-typecheck` — passed
+- All existing interactions preserved (click, dblclick, contextmenu, drag events unchanged)
+- Phantom track rendering still uses warning icon / path / action button layout, spanning full grid width