Improve delegate tool support in the TUI

[zatevakhin]

Summary

Improve how delegate tool calls are displayed in the QueryMT TUI.

Current behavior

The TUI currently recognizes delegate tool calls, but only shows a simple one-line summary based on the objective.

Problem

Delegation is more complex than many other tools and likely needs richer presentation. Compared with tools like edit, write_file, and shell, the current delegate rendering does not expose enough useful context or outcome information.

Expected behavior

When a delegate tool call appears, the TUI should display delegation details in a more useful way, such as:

• delegated objective/task
• selected agent, if available
• useful result or outcome summary
• error state, if delegation fails

Notes

There is already a minimal delegate summary path in the codebase, so this issue is about richer and more complete TUI support rather than first-time recognition.