fix: build Python package in isolation

.github/workflows/backend-quality-gate.yml

@@ -63,7 +63,7 @@ jobs:
           python scripts/run_quality_gate.py \
             --profile quick --skip-yoga-logic --skip-frontend-runtime \
             2>&1 | tee artifacts/quick-quality-gate.log
-          python -m build --no-isolation
+          python -m build
 
       - name: Upload quick quality gate diagnostics
         if: always()

frontend/tests/staging-backend-workflows.test.ts

@@ -75,6 +75,13 @@ test("quality gate validates relevant changes once and publishes a digest manife
   assert.doesNotMatch(workflow, /(?:^|:)latest$/m);
 });
 
+test("quality gate builds the Python package with its declared backend dependencies", () => {
+  const workflow = read(qualityWorkflow);
+
+  assert.match(workflow, /^\s+python -m build$/m);
+  assert.doesNotMatch(workflow, /python -m build --no-isolation/);
+});
+
 test("deployment test command includes manifest behavior coverage", () => {
   const packageJson = JSON.parse(
     readFileSync(new URL("../package.json", import.meta.url), "utf8"),