feat: add CI workflow, lifecycle integration tests, and mark completed plan items

- Add GitHub Actions CI: test, typecheck, lint on push/PR to main
- Add fight lifecycle integration tests: full pipeline, ELO advantage,
  combo scaling, type exhaustion, answer verification (7 tests)
- Kaplay already lazy-loaded via route-level code splitting
- Total: 135 tests across 7 test files

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

.github/workflows/ci.yml

@@ -0,0 +1,35 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: pnpm
+
+      - run: pnpm install --frozen-lockfile
+
+      - name: Tests
+        run: pnpm test -- --run
+
+      - name: Type check
+        run: |
+          pnpm --filter server exec tsc --noEmit
+          pnpm --filter frontend exec vue-tsc --noEmit
+
+      - name: Lint
+        run: pnpm lint