fix(tui): surface nested subagent prompts

[feddericovonwernich]

Issue for this PR

Closes #13715

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

The root TUI session only surfaced permission/question requests from direct child sessions, so prompts from deeper nested subagent sessions could hang without being shown.

This PR adds descendant-aware request selection (root-first traversal) and wires it into the TUI session route. It also adds regression tests at selector level and sync-provider integration level to cover nested prompt surfacing.

How did you verify your code works?

• Reproduced with red/green flow:
  • temporarily reverted traversal logic and confirmed nested-grandchild tests fail
  • restored fix and confirmed tests pass
• Ran locally:
  • bun test test/cli/tui/session-request-tree.test.ts
  • bun test test/cli/tui/sync-provider.test.tsx
• Compiled and tested locally with the built binary; nested prompt surfacing works in live usage.

Screenshots / recordings

N/A (logic + tests change; no UI layout/styling change)

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found one potentially related PR:

Related PR:

• fix: render permission and question prompts from nested subagent session #13719: "fix: render permission and question prompts from nested subagent session"
  • fix: render permission and question prompts from nested subagent session #13719
  • This PR addresses a similar issue with rendering prompts from nested subagent sessions. According to the current PR description, fix: render permission and question prompts from nested subagent session #13719 has similar scope but the current PR (21996) adds additional regression test coverage.

The current PR #21996 is explicitly mentioned as being related to #13719 and appears to be a follow-up or enhancement with broader test coverage for nested subagent prompt handling. They're addressing related but distinct aspects of the same feature area.

[github-actions]

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