fix(subagent): remove permission.question=deny override that caused zombie sessions

Child session creation was injecting permission: { question: 'deny' } which
conflicted with OpenCode's child session permission handling, causing subagent
sessions to hang with 0 messages after creation (zombie state).

Remove the permission override from all session creators (BackgroundManager,
sync-session-creator, call-omo-agent) and rely on prompt-level tool restrictions
(tools.question=false) to maintain the intended policy.

Closes #1711

src/features/background-agent/spawner/background-session-creator.ts

@@ -15,7 +15,6 @@ export async function createBackgroundSession(options: {
   const body = {
     parentID: input.parentSessionID,
     title: `Background: ${input.description}`,
-    permission: [{ permission: "question", action: "deny" as const, pattern: "*" }],
   }
 
   const createResult = await client.session