fix: add build step before tests in CI

Without the "bun" export condition, workspace packages resolve to dist/
instead of src/. The test job needs to build packages first so dist/
exists when tests import from workspace dependencies like repterm-api.

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

Author: cnbailian

.github/workflows/build.yml

@@ -80,6 +80,9 @@ jobs:
       - name: Install dependencies
         run: bun install --frozen-lockfile
 
+      - name: Build all packages
+        run: bun run build
+
       - name: Run tests
         run: bun run test