ci: add PR build check workflow and PR template

- Add build.yml workflow that runs npm run build on PRs to main/dev
- Add PR template with summary, type, changes, test plan sections
- Required by branch protection rules on main

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

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,31 @@
+## Summary
+
+<!-- Briefly describe what this PR does and why -->
+
+## Type of Change
+
+- [ ] Feature (new functionality)
+- [ ] Bug fix
+- [ ] Refactor (no functional change)
+- [ ] Docs
+- [ ] CI/CD
+- [ ] Other
+
+## Changes
+
+<!-- List the key changes made -->
+
+## Test Plan
+
+<!-- How did you test? What should reviewers verify? -->
+
+- [ ] Build passes (`npm run build`)
+- [ ] Tested manually
+
+## Screenshots (if applicable)
+
+<!-- Add screenshots for UI changes -->
+
+## Related Issues
+
+<!-- Link related issues, e.g. Closes #123 -->

.github/workflows/build.yml

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+name: Build
+
+on:
+  pull_request:
+    branches:
+      - main
+      - dev
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Build
+        run: npm run build