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/task-starter.ts

@@ -69,7 +69,6 @@ export async function startQueuedTask(args: {
     body: {
       parentID: input.parentSessionID,
       title: `${input.description} (@${input.agent} subagent)`,
-      permission: [{ permission: "question", action: "deny" as const, pattern: "*" }],
     } as any,
     query: {
       directory: parentDirectory,