fix(pi): converge worker failures and thinking state

tests/unit/pi-subagent-child.test.ts

@@ -147,8 +147,8 @@ describe('managed Pi subagent child opener', () => {
       summary: 'managed child summary',
       usage: { inputTokens: 7, outputTokens: 11, cacheReadTokens: 2 },
     });
-    await readOnly.stop();
-    await coding.stop();
+    await readOnly.stop('test_injection');
+    await coding.stop('test_injection');
     expect(processes.every(({ stopped }) => stopped)).toBe(true);
     await host.close();
   });
@@ -210,8 +210,8 @@ describe('managed Pi subagent child opener', () => {
     expect(await readFile(path.join(userDataDir, 'coding-runtime', 'pi', 'config', 'models.json'), 'utf8'))
       .not.toContain('host-token-');
 
-    await first.stop();
-    await second.stop();
+    await first.stop('test_injection');
+    await second.stop('test_injection');
     await host.close();
   });
 });