feat(subagent): block question tool at both SDK and hook level

- Add permission: [{ permission: 'question', action: 'deny' }] to session.create()
  in background-agent and delegate-task for SDK-level blocking
- Add subagent-question-blocker hook as backup layer to intercept question tool
  calls in tool.execute.before event
- Ensures subagents cannot ask questions to users and must work autonomously

src/features/background-agent/manager.ts

@@ -224,7 +224,10 @@ export class BackgroundManager {
       body: {
         parentID: input.parentSessionID,
         title: `Background: ${input.description}`,
-      },
+        permission: [
+          { permission: "question", action: "deny" as const, pattern: "*" },
+        ],
+      } as any,
       query: {
         directory: parentDirectory,
       },