fix: resolve media detail from sessions when lifetime summary is absent

- Change `getMediaDetail` JOIN to LEFT JOIN on `imm_lifetime_media` and fall back to aggregated session metrics when no lifetime row exists
- Add filter `AND (lm.video_id IS NOT NULL OR s.session_id IS NOT NULL)` to keep results valid
- Add regression test covering the session-visible / media-detail-missing mismatch

backlog/tasks/task-346 - Fix-stats-session-detail-when-recent-media-is-missing.md

@@ -0,0 +1,57 @@
+---
+id: TASK-346
+title: Fix stats session detail when recent media is missing
+status: Done
+assignee:
+  - Codex
+created_date: '2026-05-12 06:41'
+updated_date: '2026-05-12 06:44'
+labels:
+  - bug
+  - stats
+dependencies: []
+priority: high
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+Stats overview can show a completed session, but clicking it opens a detail view that says "Media not found". The details view should resolve the session/media consistently for recently completed local playback so users can inspect session cards, words, timeline, and media stats after a video finishes.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [x] #1 A completed session listed on the stats overview opens a usable details view instead of "Media not found" when its media is still present in stats data.
+- [x] #2 Regression coverage reproduces the overview-to-detail lookup mismatch and verifies the corrected behavior.
+- [x] #3 Relevant stats/detail documentation is updated if behavior or APIs change.
+<!-- AC:END -->
+
+## Implementation Plan
+
+<!-- SECTION:PLAN:BEGIN -->
+1. Add a focused regression test in `src/core/services/immersion-tracker/__tests__/query.test.ts` covering a video/session visible from session summaries before `imm_lifetime_media` exists.
+2. Update `getMediaDetail` in `src/core/services/immersion-tracker/query-library.ts` so detail rows can resolve from `imm_videos` plus session metrics when lifetime summary is absent.
+3. Run the focused query test lane and update task notes/acceptance criteria.
+<!-- SECTION:PLAN:END -->
+
+## Implementation Notes
+
+<!-- SECTION:NOTES:BEGIN -->
+Implemented root-cause fix in `getMediaDetail`: media detail now resolves from `imm_videos` plus session metrics when `imm_lifetime_media` is not populated yet, while still preferring lifetime summary totals when available. Added regression test for session-visible/media-detail-missing mismatch. No docs update required because the API shape is unchanged; added changelog fragment `changes/346-stats-session-detail.md`. Verification: `bun test src/core/services/immersion-tracker/__tests__/query.test.ts`, `bun run typecheck`, `bun run format:check:src`, `bun run test:fast`, `bun run changelog:lint`.
+<!-- SECTION:NOTES:END -->
+
+## Final Summary
+
+<!-- SECTION:FINAL_SUMMARY:BEGIN -->
+Summary:
+- Fixed stats media detail lookup so sessions visible in overview can open detail even before lifetime media summaries exist.
+- Preserved lifetime-summary totals when available and added a regression test for the missing-lifetime case.
+- Added `changes/346-stats-session-detail.md` for the user-visible fix.
+
+Tests:
+- `bun test src/core/services/immersion-tracker/__tests__/query.test.ts`
+- `bun run typecheck`
+- `bun run format:check:src`
+- `bun run test:fast`
+- `bun run changelog:lint`
+<!-- SECTION:FINAL_SUMMARY:END -->