[BUG] Parent agent has no visibility into user rejections/feedback to subagent tool calls

Description

When a subagent (spawned via the Agent tool) has a tool call rejected by the user — potentially with a question or feedback message — the parent agent has no visibility into this interaction. The parent only receives the subagent's final result, which may or may not reflect the user's feedback.

Steps to reproduce

1. Have the parent agent spawn a subagent (e.g., subagent_type: engineer) to perform file edits
2. When the subagent attempts a tool call (e.g., Edit), reject it with a question like "why are you changing this?"
3. The subagent sees the rejection and may adapt, but the parent agent is never notified
4. The parent agent's final summary has no awareness of the user's concern

Expected behavior

The parent agent should be informed when the user rejects a subagent's tool call, especially when the user provides feedback or asks a question. This is critical because:

• The user may be course-correcting the approach, and only the subagent sees it
• The parent may re-delegate the same flawed approach if it doesn't learn
• The user has no way to communicate back to the parent through the subagent interaction

Actual behavior

The parent agent receives only the subagent's final output. All mid-flight user rejections, questions, and feedback are invisible to the parent. The user's only recourse is to wait for the subagent to finish and then re-explain the issue to the parent.

Environment

• Claude Code CLI on macOS
• Using Agent tool with subagent_type: engineer
• Foreground agent (not background)