refactor: identify and freeze messages at creation

packages/subagent/subagent-dsh-sdk/src/run.ts

@@ -170,7 +170,7 @@ export async function startSdkRun(request: SubagentStartRequest, spec: SdkRunSpe
     if (event.type === 'assistant/chunk' && event.data.chunk.type === 'text-delta') {
       partial.push(event.data.chunk.text)
     } else if (event.type === 'assistant/message') {
-      lastMessage = event.data.content
+      lastMessage = event.data.message.content
     }
   }
   const collectOutput = (): ContentBlock[] => {

packages/subagent/subagent-dsh-sdk/tests/loader-composition.e2e.ts

@@ -91,7 +91,7 @@ describe('SDK subagent cwd inheritance through a real cordis.yml', () => {
     // process's launch directory.
     const results = events.filter(event => event.type === 'tool/result')
     expect(results).toHaveLength(1)
-    const resultText = results[0]!.data.content
+    const resultText = results[0]!.data.message.content[0].content
       .filter(block => block.type === 'text')
       .map(block => block.text)
       .join('')