fix(tui): surface subagent permissions and questions - #44976

Summary

• Show permission and question prompts from child and nested subagent sessions without leaving their session view.
• Identify the requesting agent/task, show pending request position, and preserve an in-progress question when another request arrives.
• Notify for child permission/question requests while keeping routine subagent lifecycle notifications unchanged.

Closes #43413

Testing

• bun test in packages/tui (801 passed, 5 existing skips)
• bun test test/component/session-tabs-mouse.test.tsx --rerun-each 30 in packages/tui (180 passed)
• bun test in packages/cli (218 passed before syncing latest v2)
• bun typecheck in packages/tui and packages/cli
• Pre-push workspace typecheck (32 packages)