Fix CI: use bun run test to split unit/fixture tests correctly

CI was running `bun test` which ran jsdom fixture tests in bun, causing
timeouts. Now uses `bun run test` which runs unit tests in bun and fixture
tests in node.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -14,16 +14,21 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
         
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+
       - name: Setup Bun
         uses: oven-sh/setup-bun@v2
         with:
           bun-version: latest
-      
+
       - name: Install dependencies
         run: bun install
-        
+
       - name: Run tests
-        run: bun test
+        run: bun run test
         
       - name: Build
         run: bun run build