ci: re-enable file parallelism, remove per-file leak diagnostic

Investigation complete: the lingering handles are native (koffi/FFI) and
invisible to JS instrumentation. Restore plain parallel 'npm test' on the
inprocess legs and drop the single-worker leak-by-file tracer.

Author: SteveSandersonMS

.github/workflows/nodejs-sdk-tests.yml

@@ -80,14 +80,8 @@ jobs:
         if: matrix.transport == 'inprocess'
         run: |
           echo "COPILOT_SDK_DEFAULT_CONNECTION=inprocess" >> "$GITHUB_ENV"
-          echo "VITEST_LEAK_BY_FILE=1" >> "$GITHUB_ENV"
 
       - name: Run Node.js SDK tests
         env:
           COPILOT_HMAC_KEY: ${{ secrets.COPILOT_DEVELOPER_CLI_INTEGRATION_HMAC_KEY }}
-        run: |
-          if [ "${{ matrix.transport }}" = "inprocess" ]; then
-            npm test -- --no-file-parallelism --reporter=default --reporter=hanging-process
-          else
-            npm test
-          fi
+        run: npm test

nodejs/test/diagnostics/leakByFile.ts

@@ -9,8 +9,6 @@ export default defineConfig({
         teardownTimeout: 10000,
         isolate: true, // Run each test file in isolation
         pool: "forks", // Use process forking for better isolation
-        setupFiles:
-            process.env.VITEST_LEAK_BY_FILE === "1" ? ["./test/diagnostics/leakByFile.ts"] : [],
         // Exclude our ad-hoc test files that aren't vitest-based
         exclude: [
             "**/node_modules/**",