feat: Add unit test step to QA skill workflow

Step 6 now writes Vitest unit tests for non-trivial hooks and utility
functions before E2E tests. Includes clear guidance on what to test
(custom hooks, pure functions, form validation) and what to skip
(presentational components, logic covered by E2E). Steps 6-9 renumbered.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/qa/SKILL.md

@@ -64,7 +64,26 @@ npm run test:e2e          # Playwright: E2E tests from previous QA runs
 ```
 Note any failures — these are regressions and must be treated as High bugs.
 
-### 6. Write E2E Tests
+### 6. Write Unit Tests
+Before E2E tests, identify and test isolated logic with Vitest in `src/__tests__/PROJ-X-*.test.ts`:
+
+**What to unit test (evaluate each):**
+- Custom hooks with non-trivial logic (e.g. `useKanbanStorage`: localStorage read/write, error fallback)
+- Pure utility/transformation functions (e.g. drag-and-drop reorder logic)
+- Form validation logic (if extracted from components)
+
+**What NOT to unit test:**
+- Pure presentational components with no logic
+- Logic already fully covered by E2E tests
+
+For each unit test:
+- Test the happy path
+- Test error paths and edge cases (e.g. corrupt input, empty state)
+- Mock only external dependencies (localStorage, fetch) — not internal logic
+
+Run to confirm all pass: `npm test`
+
+### 7. Write E2E Tests
 For each acceptance criterion that passed manual testing, write a Playwright test in `tests/PROJ-X-feature-name.spec.ts`:
 - One `test()` per acceptance criterion
 - Tests describe the user journey in plain language
@@ -72,11 +91,11 @@ For each acceptance criterion that passed manual testing, write a Playwright tes
 
 These tests become the permanent regression suite for this feature.
 
-### 7. Document Results
+### 8. Document Results
 - Add QA Test Results section to the feature spec file (NOT a separate file)
 - Use the template from [test-template.md](test-template.md)
 
-### 8. User Review
+### 9. User Review
 Present test results with clear summary:
 - Total acceptance criteria: X passed, Y failed
 - Bugs found: breakdown by severity
@@ -119,6 +138,8 @@ If your context was compacted mid-task:
 - [ ] Regression test on related features
 - [ ] Every bug documented with severity + steps to reproduce
 - [ ] Screenshots added for visual bugs
+- [ ] Unit tests written for non-trivial hooks and utility functions (`npm test` passes)
+- [ ] E2E tests written for all passing acceptance criteria (`npm run test:e2e` passes)
 - [ ] QA section added to feature spec file
 - [ ] User has reviewed results and prioritized bugs
 - [ ] Production-ready decision made