feat: add Vitest testing setup with 57 passing tests

.github/workflows/ci.yml

@@ -0,0 +1,27 @@
+name: CI
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+          cache: npm
+      - run: npm ci --legacy-peer-deps
+      - run: npm run typecheck
+      - run: npm run test:coverage
+      - name: Post coverage comment on PR
+        if: github.event_name == 'pull_request'
+        uses: davelosert/vitest-coverage-report-action@v2

.gitignore

@@ -1,6 +1,4 @@
-<<<<<<< HEAD
-.DS_Storeassets/*.gif
 .DS_Store
-=======
-.DS_Store
->>>>>>> origin/main
+assets/*.gif
+node_modules/
+coverage/