fix: address PR #57 CodeRabbit feedback

- Acquire AniList post-watch in-flight lock before async gating to prevent duplicate writes
- Isolate manual watched mark result from AniList post-watch callback failures
- Report known-word cache clears as mutations during immediate append when state existed
- Add regression tests for each fix

backlog/tasks/task-334 - Assess-and-address-PR-57-latest-CodeRabbit-comments.md

@@ -0,0 +1,53 @@
+---
+id: TASK-334
+title: Assess and address PR 57 latest CodeRabbit comments
+status: Done
+assignee:
+  - '@codex'
+created_date: '2026-05-04 05:03'
+updated_date: '2026-05-04 05:07'
+labels:
+  - pr-feedback
+  - coderabbit
+dependencies: []
+references:
+  - 'https://github.com/ksyasuda/SubMiner/pull/57'
+priority: medium
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+Assess the latest CodeRabbit review on PR #57 submitted 2026-05-04 and fix verified issues. Current scope: AniList post-watch duplicate-write race, known-word cache mutation return value, and manual-mark AniList rejection isolation with regression coverage.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [x] #1 Each latest CodeRabbit comment is either fixed or explicitly assessed as not applicable against current code.
+- [x] #2 Regression tests cover behavior changes where practical.
+- [x] #3 Relevant focused tests and typecheck pass, or any blocked verification is documented.
+<!-- AC:END -->
+
+## Implementation Plan
+
+<!-- SECTION:PLAN:BEGIN -->
+1. Verify each latest CodeRabbit finding against current code.
+2. Update known-word cache append return semantics so cache clears are reported as mutations when state existed.
+3. Acquire AniList post-watch in-flight before async gating and release in finally.
+4. Isolate manual-mark AniList callback failures in IPC and add a rejection-path regression test.
+5. Run focused tests for touched areas plus typecheck; document any blocked verification.
+<!-- SECTION:PLAN:END -->
+
+## Implementation Notes
+
+<!-- SECTION:NOTES:BEGIN -->
+Verified latest CodeRabbit review submitted 2026-05-04 on PR #57. Fixed all three current items: known-word cache mutation return after cache reset, AniList post-watch concurrent in-flight race, and manual watched mark isolation from AniList callback failures. Added regression tests for each path and a changelog fragment.
+<!-- SECTION:NOTES:END -->
+
+## Final Summary
+
+<!-- SECTION:FINAL_SUMMARY:BEGIN -->
+Fixed latest PR #57 CodeRabbit feedback by reporting known-word cache clears as mutations during immediate append, acquiring AniList post-watch in-flight before awaited gates to prevent duplicate writes, and isolating manual watched mark success from AniList post-watch callback failures. Added focused regression coverage in known-word cache, AniList post-watch, and IPC tests, plus a changelog fragment.
+
+Verification: bun test src/anki-integration/known-word-cache.test.ts; bun test src/main/runtime/anilist-post-watch.test.ts; bun test src/core/services/ipc.test.ts; bun run typecheck; bun run format:check:src; bun run changelog:lint; bun run test:fast; bun run test:env; bun run build; bun run test:smoke:dist.
+<!-- SECTION:FINAL_SUMMARY:END -->