docs(09-01): complete Vitest infrastructure plan

Tasks completed: 3/3
- Install Vitest dependencies and configure multi-project setup
- Create SvelteKit module mocks in setup file
- Write sample test to verify infrastructure

SUMMARY: .planning/phases/09-ci-pipeline/09-01-SUMMARY.md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.planning/phases/09-ci-pipeline/09-01-SUMMARY.md

@@ -0,0 +1,105 @@
+---
+phase: 09-ci-pipeline
+plan: 01
+subsystem: testing
+tags: [vitest, playwright, svelte5, coverage, browser-testing]
+
+# Dependency graph
+requires:
+  - phase: 01-foundation
+    provides: SvelteKit project structure with vite.config.ts
+provides:
+  - Multi-project Vitest configuration (browser + node modes)
+  - SvelteKit module mocks ($app/navigation, $app/stores, $app/environment)
+  - Test scripts (test, test:unit, test:coverage)
+  - Coverage reporting with v8 provider
+affects: [09-02, 09-03]
+
+# Tech tracking
+tech-stack:
+  added: [vitest@4.0.18, @vitest/browser, @vitest/browser-playwright, vitest-browser-svelte, @vitest/coverage-v8]
+  patterns: [multi-project-test-config, sveltekit-module-mocking]
+
+key-files:
+  created:
+    - vitest-setup-client.ts
+    - src/lib/utils/filterEntries.test.ts
+  modified:
+    - vite.config.ts
+    - package.json
+
+key-decisions:
+  - "Multi-project setup: browser (client) vs node (server) test environments"
+  - "Coverage thresholds with autoUpdate initially (no hard threshold yet)"
+  - "SvelteKit mocks use simple vi.mock, not importOriginal (avoids SSR issues)"
+
+patterns-established:
+  - "*.svelte.test.ts for component tests (browser mode)"
+  - "*.test.ts for utility/server tests (node mode)"
+  - "Test factory functions for creating test data"
+
+# Metrics
+duration: 3min
+completed: 2026-02-03
+---
+
+# Phase 9 Plan 1: Vitest Infrastructure Summary
+
+**Multi-project Vitest configuration with browser mode for Svelte 5 components and node mode for server/utility tests**
+
+## Performance
+
+- **Duration:** 3 min
+- **Started:** 2026-02-03T22:27:09Z
+- **Completed:** 2026-02-03T22:29:58Z
+- **Tasks:** 3
+- **Files modified:** 4
+
+## Accomplishments
+- Vitest installed and configured with multi-project setup
+- Browser mode ready for Svelte 5 component tests (via Playwright)
+- Node mode ready for server/utility tests
+- SvelteKit module mocks ($app/*) for test isolation
+- Coverage reporting functional (v8 provider, autoUpdate thresholds)
+- 17 unit tests proving infrastructure works
+
+## Task Commits
+
+Each task was committed atomically:
+
+1. **Task 1: Install Vitest dependencies and configure multi-project setup** - `a3ef94f` (feat)
+2. **Task 2: Create SvelteKit module mocks in setup file** - `b0e8e4c` (feat)
+3. **Task 3: Write sample test to verify infrastructure** - `b930f18` (test)
+
+## Files Created/Modified
+- `vite.config.ts` - Multi-project Vitest config (client browser mode + server node mode)
+- `vitest-setup-client.ts` - SvelteKit module mocks for browser tests
+- `package.json` - Test scripts (test, test:unit, test:unit:watch, test:coverage)
+- `src/lib/utils/filterEntries.test.ts` - Sample unit test with 17 test cases, 100% coverage
+
+## Decisions Made
+- Used v8 coverage provider (10x faster than istanbul, equally accurate since Vitest 3.2)
+- Set coverage thresholds to autoUpdate initially - Plan 02 will enforce 80% threshold
+- Browser mode uses Playwright provider (real browser via Chrome DevTools Protocol)
+- SvelteKit mocks are simple vi.fn() implementations, not importOriginal (causes SSR issues per research)
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Issues Encountered
+
+None
+
+## User Setup Required
+
+None - no external service configuration required.
+
+## Next Phase Readiness
+- Test infrastructure ready for Plan 02 (coverage thresholds, CI integration)
+- Component test infrastructure ready but no component tests yet (Plan 03 scope)
+- filterEntries.test.ts demonstrates node-mode test pattern
+
+---
+*Phase: 09-ci-pipeline*
+*Completed: 2026-02-03*