fix: propagate parent agent permissions to subagent child sessions

[brittlewis12]

Fixes #12566

What does this PR do?

Subagents don’t respect the parent agent's permission rules, instead using their own restrictive defaults. Any tool call evaluating to 'ask' would block indefinitely, even when explicitly configured to run unattended.

This fix includes the parent agent’s permission rules in the child session, before the hard-coded denies (todowrite, todoread, task) so findLast respects the override order correctly.

How did you verify your code works?

wrote a regression test, saw it fail, and then made it pass.

[github-actions]

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

Based on my search, I found several related PRs that address subagent permission issues. Here are the potentially relevant ones (excluding the current PR #12584):

Related PRs:

1. fix: prevent subagent permission bypass via tools field inheritance #7473 - fix: prevent subagent permission bypass via tools field inheritance

   • Directly related to subagent permission handling and preventing permission bypasses

2. feat(task): Add subagent-to-subagent delegation with budgets, persistent sessions, and hierarchical session navigation #7756 - feat(task): Add subagent-to-subagent delegation with budgets, persistent sessions, and hierarchical session navigation

   • Addresses subagent-to-subagent delegation and session management, which relates to the permission inheritance chain

3. fix(acp): handle permission requests from child sessions #12136 - fix(acp): handle permission requests from child sessions

   • Directly handles permissions for child sessions, potentially overlapping with the current fix

4. fix(questions): fixes #7654 where sub-sub agents can't ask questions #10539 - fix(questions): fixes #7654 where sub-sub agents can't ask questions

   • Addresses permission/capability issues in nested subagent scenarios

Important: Check if #12136 (handle permission requests from child sessions) might be addressing the same underlying issue as #12584, as both deal with child session permissions.