docs(14-02): complete view caching navigation plan

- Created 14-02-SUMMARY.md with execution results
- Updated STATE.md with Phase 14 position and decisions
- Updated ROADMAP.md progress for Phase 14 (1/4 plans)

.planning/ROADMAP.md

@@ -120,7 +120,7 @@ Plans:
   3. Render hot paths (renderTrackRow, renderTrackItem) create zero new closures per frame — all event handling uses delegation
   4. Store notifications are batched (queueMicrotask) and components only re-render when their relevant data changes
   5. A profiling guide documents how to diagnose performance issues using pprof (backend) and DevTools (frontend)
-**Plans:** 4 plans
+**Plans:** 1/4 plans executed
 Plans:
 - [ ] 14-01-PLAN.md — CSS containment + GPU layer promotion on all scroll containers
 - [ ] 14-02-PLAN.md — View caching navigation system (replace innerHTML destruction)
@@ -144,7 +144,7 @@ Plans:
 | 11. Per-Library Scan Pipeline | 3/3 | Complete    | 2026-03-09 | - |
 | 12. Library CRUD & Data Integrity | v1.1 | 1/2 | In Progress | - |
 | 13. Library Views & Phantom Tracks | v1.1 | 0/? | Not started | - |
-| 14. Performance Optimization | v1.1 | 0/4 | Not started | - |
+| 14. Performance Optimization | 1/4 | In Progress|  | - |
 
 ---
 *Roadmap created: 2026-02-27*

.planning/STATE.md

@@ -18,15 +18,15 @@ progress:
 See: .planning/PROJECT.md (updated 2026-03-08)
 
 **Core value:** The music player works reliably and feels solid — every interaction is correct, responsive, and trustworthy.
-**Current focus:** v1.1 Multi-Library Support — Phase 11 (Per-Library Scan Pipeline)
+**Current focus:** v1.1 Multi-Library Support + Performance Optimization
 
 ## Current Position
 
-Phase: 12 — Library CRUD & Data Integrity
+Phase: 14 — Performance Optimization
-Plan: 1 of 2 in Phase (Plan 01 complete)
+Plan: 1 of 4 in Phase (Plan 02 complete)
-Status: Plan 12-01 complete — backend CRUD API implemented
+Status: Plan 14-02 complete — view caching navigation system
-Progress: ████████████████░░░░ 3/5 phases complete (Phase 12 in progress)
+Progress: ████████████████░░░░ Phase 14 in progress (1/4 plans)
-Last activity: 2026-03-12 — Completed 12-01 library CRUD backend API
+Last activity: 2026-03-14 — Completed 14-02 view caching navigation
 
 ### Phase Overview
 
@@ -37,6 +37,7 @@ Last activity: 2026-03-12 — Completed 12-01 library CRUD backend API
 | 11. Per-Library Scan Pipeline | Complete (3/3 plans) ✅ |
 | 12. Library CRUD & Data Integrity | In progress (1/2 plans) |
 | 13. Library Views & Phantom Tracks | Not started |
+| 14. Performance Optimization | In progress (1/4 plans) |
 
 ## Performance Metrics
 
@@ -56,6 +57,7 @@ Last activity: 2026-03-12 — Completed 12-01 library CRUD backend API
 | Phase 11-03 P03 | 10 min | 1 task | 3 files |
 | Phase 11-02 P02 | 4 min | 2 tasks | 2 files |
 | Phase 12-01 P01 | 6 min | 2 tasks | 6 files |
+| Phase 14-02 P02 | 1 min | 1 task | 1 file |
 
 ## Accumulated Context
 
@@ -119,6 +121,14 @@ Decisions from v1.0 are archived in PROJECT.md Key Decisions table. Key patterns
 | Sentinel errors for all validation per err113 | errLibraryNameEmpty, errLibraryNameTooLong, errLibraryNameDuplicate, errLibraryPathNotExist |
 | Pre-populate phantom metadata BEFORE cascade delete | Avoids lost join data — playlist_tracks need track metadata after audio_files rows are gone |
 
+### Phase 14 Decisions
+
+| Decision | Rationale |
+|----------|-----------|
+| Primary views cached, detail views ephemeral | Detail views depend on entity IDs that change; caching would show stale content |
+| Inline style.display toggle over CSS class | Simpler, no specificity issues, empty string restores natural display value |
+| viewCache bounded at 6 entries | One per primary view — negligible memory since data is already in store caches |
+
 ### Warnings (carry forward)
 
 - Player lock ordering (`p.mu` before `speaker.Lock()`, goroutine dispatch in beep callback) — carry forward
@@ -144,10 +154,10 @@ Decisions from v1.0 are archived in PROJECT.md Key Decisions table. Key patterns
 
 ### Last Session
 
-**Date:** 2026-03-12
+**Date:** 2026-03-14
-**What happened:** Executed Phase 12, Plan 01 — implemented backend Library CRUD API (AddLibrary, RenameLibrary, RemoveLibrary, GetRemovalImpact) with full orphan cleanup pipeline, phantom track preservation, FTS5 rebuild, queue compaction via CompactAfterLibraryRemoval, and RemovalHooks wiring in app.go.
+**What happened:** Executed Phase 14, Plan 02 — replaced innerHTML navigation with view caching system. Primary views (tracks, albums, artists, genres, playlists, settings) are now created once and kept in DOM with display toggle instead of destruction/recreation.
-**Where we stopped:** Completed 12-01-PLAN.md — Plan 01 of Phase 12 complete
+**Where we stopped:** Completed 14-02-PLAN.md — Plan 02 of Phase 14 complete
-**Next action:** Execute Phase 12 Plan 02 (Frontend library management UI)
+**Next action:** Execute remaining Phase 14 plans (14-01 CSS containment, 14-03 store optimizations, 14-04 rendering optimizations)
 
 ---
 *State initialized: 2026-02-27*
@@ -160,4 +170,4 @@ Decisions from v1.0 are archived in PROJECT.md Key Decisions table. Key patterns
 | 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 18: add multi-column metadata display to playlist-details
-*Last updated: 2026-03-12 — Completed 12-01-PLAN.md (Phase 12 Plan 01 complete)*
+*Last updated: 2026-03-14 — Completed 14-02-PLAN.md (Phase 14 Plan 02 complete)*

.planning/phases/14-performance-optimization/14-02-SUMMARY.md

@@ -0,0 +1,99 @@
+---
+phase: 14-performance-optimization
+plan: 02
+subsystem: ui
+tags: [navigation, view-caching, dom, performance, display-toggle]
+
+# Dependency graph
+requires: []
+provides:
+  - View caching navigation system — primary views created once and visibility-toggled
+  - viewCache Map with bounded 6-entry cache for primary views
+  - Ephemeral detail view lifecycle (artist-details, playlist-details, genre-details)
+affects: [14-performance-optimization]
+
+# Tech tracking
+tech-stack:
+  added: []
+  patterns:
+    - "View cache Map<string, HTMLElement> for DOM-persistent primary views"
+    - "display:none/display:'' toggle instead of innerHTML destruction"
+    - "Ephemeral detail views (remove + create) vs cached primary views"
+
+key-files:
+  created: []
+  modified:
+    - frontend/index.ts
+
+key-decisions:
+  - "Primary views cached, detail views ephemeral — detail views depend on entity IDs that change per navigation"
+  - "Inline style.display toggle over CSS class — simpler, no specificity issues, direct JS control"
+  - "viewCache bounded at 6 entries (one per primary view) — negligible memory overhead"
+
+patterns-established:
+  - "View caching: create once, toggle visibility, never destroy primary views"
+  - "Detail view lifecycle: hide primary view, remove old detail, create new detail"
+
+requirements-completed: [PERF-NAV-01, PERF-NAV-02]
+
+# Metrics
+duration: 1min
+completed: 2026-03-14
+---
+
+# Phase 14 Plan 02: View Caching Navigation Summary
+
+**DOM-persistent view cache replacing innerHTML destruction — primary views created once and visibility-toggled for instant navigation**
+
+## Performance
+
+- **Duration:** 1 min
+- **Started:** 2026-03-14T17:43:20Z
+- **Completed:** 2026-03-14T17:44:52Z
+- **Tasks:** 1
+- **Files modified:** 1
+
+## Accomplishments
+- Replaced innerHTML-based navigation with a view caching system using a `Map<string, HTMLElement>`
+- Primary views (tracks, albums, artists, genres, playlists, settings) created once and kept in DOM
+- Navigation toggles `display:none` / `display:''` instead of destroying and recreating components
+- Detail views (artist-details, playlist-details, genre-details) remain ephemeral with proper lifecycle (remove old, create new)
+- Scroll positions naturally preserved since DOM is never destroyed
+- No virtualizer reinit, no data refetch, no cover art image reload on navigation
+
+## Task Commits
+
+Each task was committed atomically:
+
+1. **Task 1: Implement view caching navigation system** - `ad91043` (perf)
+
+## Files Created/Modified
+- `frontend/index.ts` - Replaced switch/innerHTML navigation with VIEW_TAGS map, viewCache Map, display toggle, and ephemeral detail view lifecycle
+
+## Decisions Made
+- **Primary views cached, detail views ephemeral** — Detail views (artist-details, playlist-details, genre-details) depend on entity IDs/names that change per navigation, so caching them would show stale content. Primary views are stateless navigation targets that benefit from persistence.
+- **Inline style.display toggle** — Using `element.style.display = 'none'` / `element.style.display = ''` rather than CSS classes avoids specificity issues and gives direct control. The empty string restores the element's natural display value from CSS (`.main-panel > * { height: 100% }`).
+- **viewCache bounded at 6 entries** — One entry per primary view tag in VIEW_TAGS. Memory overhead is negligible since the data each view holds is already in store caches regardless.
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Issues Encountered
+None
+
+## User Setup Required
+None - no external service configuration required.
+
+## Next Phase Readiness
+- View caching complete — ready for remaining Phase 14 plans (14-01 CSS containment, 14-03 store optimizations, 14-04 rendering optimizations)
+- Existing scroll save/restore logic in components preserved as fallback for data invalidation scenarios
+
+---
+## Self-Check: PASSED
+
+- ✅ frontend/index.ts exists
+- ✅ Commit ad91043 exists
+
+*Phase: 14-performance-optimization*
+*Completed: 2026-03-14*