fix: build SDK before running tests in CI

The test jobs run individual test files with 'bun test <file>', which bypasses
the package.json pretest hook. This caused npm-app tests to fail with 'Cannot
find module @codebuff/sdk' because the SDK wasn't built.

Changes:
- Added 'Build SDK before tests' step in test job
- Added 'Build SDK before integration tests' step in test-integration job
- This ensures SDK dist artifacts (index.mjs, index.cjs, vendor/) exist
  before tests that depend on @codebuff/sdk are executed

Root cause: CI test command bypasses npm hooks by running test files directly.

Author: brandonkachen

.github/workflows/ci.yml

@@ -130,6 +130,9 @@ jobs:
           echo "NEXT_PUBLIC_INFISICAL_UP=true" >> $GITHUB_ENV
           echo "CODEBUFF_GITHUB_TOKEN=${{ secrets.CODEBUFF_GITHUB_TOKEN }}" >> $GITHUB_ENV
 
+      - name: Build SDK before tests
+        run: cd sdk && bun run build
+
       - name: Run ${{ matrix.package }} tests
         uses: nick-fields/retry@v3
         with:
@@ -201,6 +204,9 @@ jobs:
           echo "NEXT_PUBLIC_INFISICAL_UP=true" >> $GITHUB_ENV
           echo "CODEBUFF_GITHUB_TOKEN=${{ secrets.CODEBUFF_GITHUB_TOKEN }}" >> $GITHUB_ENV
 
+      - name: Build SDK before integration tests
+        run: cd sdk && bun run build
+
       - name: Run ${{ matrix.package }} integration tests
         uses: nick-fields/retry@v3
         with: