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/tools/call-omo-agent/subagent-session-creator.test.ts

@@ -0,0 +1,47 @@
+import { describe, expect, test } from "bun:test"
+
+import { resolveOrCreateSessionId } from "./subagent-session-creator"
+import { _resetForTesting, subagentSessions } from "../../features/claude-code-session-state"
+
+describe("call-omo-agent resolveOrCreateSessionId", () => {
+  test("tracks newly created child session as subagent session", async () => {
+    // given
+    _resetForTesting()
+
+    const createCalls: Array<unknown> = []
+    const ctx = {
+      directory: "/project",
+      client: {
+        session: {
+          get: async () => ({ data: { directory: "/parent" } }),
+          create: async (args: unknown) => {
+            createCalls.push(args)
+            return { data: { id: "ses_child_sync" } }
+          },
+        },
+      },
+    }
+
+    const args = {
+      description: "sync test",
+      prompt: "hello",
+      subagent_type: "explore",
+      run_in_background: false,
+    }
+
+    const toolContext = {
+      sessionID: "ses_parent",
+      messageID: "msg_parent",
+      agent: "sisyphus",
+      abort: new AbortController().signal,
+    }
+
+    // when
+    const result = await resolveOrCreateSessionId(ctx as any, args as any, toolContext as any)
+
+    // then
+    expect(result).toEqual({ ok: true, sessionID: "ses_child_sync" })
+    expect(createCalls).toHaveLength(1)
+    expect(subagentSessions.has("ses_child_sync")).toBe(true)
+  })
+})