Speed up process-host import enforcement in CI (#27124)

Reduce import-scanner work by omitting unused AST parents and the duplicate traversal. Run the mandatory process-host import check alongside static work and explicitly join it before CI can succeed.

Update both workflow phase/enforcement contracts and migrate the newer benchmark to the public subprocess package API. Keep the original package build path, manifests, runtime, test selection, and shard count. Independent native review is clean; validation and timing evidence are in the PR.

.github/workflows/pr.yml

@@ -203,6 +203,17 @@ jobs:
         with:
           bun-version-file: config/.bun-version
 
+      - name: Check process-host imports
+        if: '!cancelled()'
+        id: process-host-imports
+        background: true
+        env:
+          PREFLIGHT_PHASE_SELECTED: ${{ needs.code_paths.outputs.static_analysis == 'true' }}
+          PREFLIGHT_PRIOR_SUCCESS: ${{ job.status == 'success' }}
+        run: |
+          if [ "$PREFLIGHT_PHASE_SELECTED" != true ] || [ "$PREFLIGHT_PRIOR_SUCCESS" != true ]; then exit 0; fi
+          pnpm run check:process-host-imports
+
       # Keep each check in its own log while sharing this runner.
       - name: Lint
         if: '!cancelled()'
@@ -268,9 +279,7 @@ jobs:
 
       - name: Check reliability gate manifest
         if: needs.code_paths.outputs.static_analysis == 'true'
-        run: |
-          pnpm run check:reliability-gates
-          pnpm run check:process-host-imports
+        run: pnpm run check:reliability-gates
 
       - name: Enforce dead design-system classes
         if: needs.code_paths.outputs.static_analysis == 'true'
@@ -443,6 +452,8 @@ jobs:
       - run: pnpm run typecheck
         if: needs.code_paths.outputs.typecheck == 'true'
 
+      - wait: process-host-imports
+
       - wait: unit-plan
 
       - uses: actions/upload-artifact@v7