feat(stats): add v1 immersion stats dashboard (#19)

backlog/tasks/task-190 - Add-hover-popups-for-session-chart-events.md

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+---
+id: TASK-190
+title: Add hover popups for session chart events
+status: Done
+assignee:
+  - Codex
+created_date: '2026-03-17 22:20'
+updated_date: '2026-03-18 05:28'
+labels:
+  - stats
+  - ui
+  - bug
+milestone: m-1
+dependencies: []
+references:
+  - stats/src/components/sessions/SessionDetail.tsx
+  - stats/src/lib/session-events.ts
+  - stats/src/hooks/useSessions.ts
+  - stats/src/lib/api-client.ts
+  - docs/plans/2026-03-17-session-event-hover-popups-design.md
+priority: medium
+ordinal: 105500
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+Add hover/focus popups to session chart event markers so pauses, seeks, lookups, and card-mine events explain themselves inline. Card-mine events should lazy-load available Anki note info and present it in a richer popup with browse affordances.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [x] #1 Hovering or focusing a session-chart marker opens an event-specific popup.
+- [x] #2 Pause, seek, and lookup popups show concise event copy derived from marker metadata.
+- [x] #3 Card-mine popups lazily fetch and cache Anki note info by note id.
+- [x] #4 Card-mine popups show a formatted fallback when note info is missing or still loading.
+- [x] #5 Regression tests cover event payload shaping and popup rendering behavior.
+<!-- AC:END -->
+
+## Implementation Plan
+
+<!-- SECTION:PLAN:BEGIN -->
+1. Add failing tests for event metadata shaping and popup content selection.
+2. Extend session-event shaping to parse payload JSON into typed marker metadata.
+3. Add lazy note-info fetch/cache state for card-mine markers.
+4. Render interactive marker overlay + custom popup in the session detail chart.
+5. Run targeted stats/core verification and update this task with the result.
+<!-- SECTION:PLAN:END -->
+
+## Outcome
+
+<!-- SECTION:OUTCOME:BEGIN -->
+Completed. Session-chart event markers now open event-specific hover/focus popups, including lazy-loaded Anki note info for card-mine events with browse affordances. Verification passed via targeted stats tests, `bun run typecheck`, and the core verification lane in `.tmp/skill-verification/subminer-verify-20260317-222545-CQzyqK`.
+<!-- SECTION:OUTCOME:END -->