chore: clear dead test and allowlist leftovers of dropped runtimes

tests/agent-frontmatter.test.cjs

@@ -216,13 +216,13 @@ describe('SPAWN: spawn type consistency', () => {
     }
   });
 
-  test('execute-phase has Copilot sequential fallback in runtime_compatibility', () => {
+  test('execute-phase has a sequential inline fallback in runtime_compatibility', () => {
     const content = fs.readFileSync(
       path.join(WORKFLOWS_DIR, 'execute-phase.md'), 'utf-8'
     );
     assert.ok(
       content.includes('sequential inline execution'),
-      'execute-phase must document sequential inline execution as Copilot fallback'
+      'execute-phase must document sequential inline execution as a fallback'
     );
     assert.ok(
       content.includes('spot-check'),