docs(11): capture phase context

.planning/phases/11-per-library-scan-pipeline/11-CONTEXT.md

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+# Phase 11: Per-Library Scan Pipeline - Context
+
+**Gathered:** 2026-03-09
+**Status:** Ready for planning
+
+<domain>
+## Phase Boundary
+
+Refactor the scan pipeline from scanning a single hardcoded directory to scanning individual libraries by ID. Add sequential scan coordination (queue) so only one library scans at a time. Update progress UI to identify which library is scanning. Existing cancel/pause/resume controls work per-library with clear scope when multiple scans are queued.
+
+Library CRUD UI is Phase 12. Library-filtered views are Phase 13. This phase only changes how scans are triggered, coordinated, and displayed.
+
+</domain>
+
+<decisions>
+## Implementation Decisions
+
+### Concurrent scan policy
+- Queue silently when a scan is requested while another is running — no confirmation dialog, no toast
+- Ignore duplicate scan requests silently (if library is already scanning or already queued, no-op)
+- Unbounded queue — no cap on queued scans (realistic library counts are low, 2-10)
+- Seamless transition between queued scans — progress UI updates to next library name, no notification
+
+### Scan trigger model
+- Auto-scan all libraries on app launch (current single-directory behavior extended to all libraries)
+- `ScanLibrary(id int64)` Wails-bound method — scans a specific library by database ID
+- `ScanAllLibraries()` Wails-bound method — queries all libraries and queues them sequentially; used by both app startup and the UI "Scan All" button
+- "Scan All Libraries" button in the UI in addition to per-library scan buttons
+
+### Progress identification
+- Library name shown in existing progress bar area: "Scanning: [Library Name] (245/1200 files)"
+- When libraries are queued, show queue count: "N libraries queued" alongside the active scan progress
+- Progress UI disappears/collapses when all scans complete (matches current behavior)
+
+### Cancel/pause scope
+- Cancel button during a queued multi-scan shows a **modal dialog** with two choices: "Cancel This Library" and "Cancel All Scanning" — no default, user must pick
+- If user cancels just the current library, the next queued library starts automatically
+- Pause freezes the current scan AND the queue — resume continues the paused library, then the queue proceeds
+- No partial scan indication needed — partially-scanned library keeps whatever files were processed, user can re-scan later
+
+### Claude's Discretion
+- Event payload format (whether scan events include library name or just ID)
+- Internal queue data structure implementation
+- Exact progress bar label formatting and layout
+- How "Scan All" button is placed in the UI (this phase focuses on the button existing; Phase 12 designs the full library management UI)
+
+</decisions>
+
+<specifics>
+## Specific Ideas
+
+- The scan queue coordinator should be a separate concern from the scan execution itself — clean separation between "what to scan next" and "how to scan"
+- Cancel dialog should feel similar to the existing cancel confirmation from Phase 9, extended with the scope choice
+- Auto-scan on launch should use the same `ScanAllLibraries()` codepath as the UI button — single implementation
+
+</specifics>
+
+<deferred>
+## Deferred Ideas
+
+None — discussion stayed within phase scope
+
+</deferred>
+
+---
+
+*Phase: 11-per-library-scan-pipeline*
+*Context gathered: 2026-03-09*