test: add vitest suite + GitHub Actions CI

14 unit tests covering the BM25 re-ranker (identifier split, path-boost ordering,
zero-score drop) and repo-URL parsing (shorthand, scheme-less, branch pin, host
rejection). CI runs lint + tsc + test + build on push/PR to main.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: manojmallick

.github/workflows/ci.yml

@@ -0,0 +1,29 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+      - run: npm ci
+      - name: Lint
+        run: npm run lint
+      - name: Type check
+        run: npx tsc --noEmit
+      - name: Test
+        run: npm test
+      - name: Build
+        run: npm run build
+        env:
+          # Build must succeed without secrets; runtime features read these at request time.
+          GEMINI_API_KEY: ""