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

backlog/tasks/task-191 - Assess-PR-19-CodeRabbit-review-follow-ups.md

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+---
+id: TASK-191
+title: 'Assess PR #19 CodeRabbit review follow-ups'
+status: Done
+assignee:
+  - codex
+created_date: '2026-03-17 23:15'
+updated_date: '2026-03-17 23:18'
+labels:
+  - pr-review
+  - stats
+  - immersion-tracker
+milestone: m-1
+dependencies: []
+references:
+  - src/core/services/immersion-tracker-service.ts
+  - src/core/services/immersion-tracker-service.test.ts
+priority: medium
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+Validate the open CodeRabbit review comments on PR #19 against the current branch, implement only the confirmed fixes, and record which bot suggestions are stale or technically incomplete.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [x] #1 Each open CodeRabbit PR #19 comment is validated against the current branch behavior
+- [x] #2 Confirmed issues are fixed with regression coverage where it fits
+- [x] #3 Non-actionable or partially-wrong bot guidance is documented explicitly
+<!-- AC:END -->
+
+## Implementation Plan
+
+<!-- SECTION:PLAN:BEGIN -->
+1. Inspect the open CodeRabbit review threads on PR #19 and restate each finding in codebase terms.
+2. Add failing regression tests for any verified bugs before changing production code.
+3. Patch the smallest safe service-layer behavior, rerun focused verification, and record which suggestions were accepted versus rejected.
+<!-- SECTION:PLAN:END -->
+
+## Implementation Notes
+
+<!-- SECTION:NOTES:BEGIN -->
+Validated the two open CodeRabbit inline findings on PR #19 against the current branch. Both reported real bugs in `ImmersionTrackerService`, but the first suggestion's exact remediation was incomplete for this codebase.
+
+`reassignAnimeAnilist` did overwrite `imm_anime.description` with `NULL` when callers omitted `description`. Fixed with a presence-aware SQL update that preserves the existing description when the field is omitted while still allowing explicit `description: null` to clear the stored value. Rejected the bot's `COALESCE(?, description)` prompt because that would silently remove the explicit-clear behavior the API already supports.
+
+`ensureCoverArt` could return `true` after a fetcher reported success even when no cover-art row/blob was stored, because `undefined !== null` evaluated truthy through optional chaining. Fixed by loading the row into a local variable and requiring a non-null blob.
+
+Added regression coverage in `src/core/services/immersion-tracker-service.test.ts` for omitted-description preservation, explicit-null clearing, and the no-row `ensureCoverArt` false-positive case.
+
+Verification passed:
+- `bun test src/core/services/immersion-tracker-service.test.ts`
+- `bash .agents/skills/subminer-change-verification/scripts/classify_subminer_diff.sh src/core/services/immersion-tracker-service.ts src/core/services/immersion-tracker-service.test.ts`
+- `bash .agents/skills/subminer-change-verification/scripts/verify_subminer_change.sh --lane core src/core/services/immersion-tracker-service.ts src/core/services/immersion-tracker-service.test.ts`
+
+Verifier artifact directory: `.tmp/skill-verification/subminer-verify-20260317-231743-wHFNnN`
+<!-- SECTION:NOTES:END -->
+
+## Final Summary
+
+<!-- SECTION:FINAL_SUMMARY:BEGIN -->
+Assessed the open PR #19 CodeRabbit comments and fixed the two confirmed service-layer regressions. `reassignAnimeAnilist` now preserves an existing anime description when callers omit the `description` field but still clears it on explicit `null`, and `ensureCoverArt` no longer reports success when no cover-art row/blob exists after a fetch attempt.
+
+Both comments were actionable, but one bot-proposed fix was not correct as written for this branch: replacing the description update with `COALESCE(?, description)` would have broken intentional description clearing. Added regression tests for the accepted behaviors and verified the change with the full touched service test file plus the SubMiner `core` verification lane.
+<!-- SECTION:FINAL_SUMMARY:END -->