[FEATURE] [UI] Distinguish subagent and main agent actions/steps

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

This screenshot shows me prompting claude to do something.

• Claude spawns subagent at this line: Agent:Find BQ table auto-create/sync pattern
• Subagent executes various commands like Read tasks.py or Read bigquery_loader.py
• I can't distinguish in this UI if it's subagent doing all of this or if it's the main agent doing this (and it's doing it in parallel with subagent)

I'm using Claude Code VSCode extension v2.1.70

<img width="633" height="694" alt="Image" src="https://github.com/user-attachments/assets/df6658e0-a5b0-475a-b43b-dbbcc6698210" />

Proposed Solution

The UI should clearly distinguish steps taken by subagent from steps taken by main agent.
E.g. by including subagent _name_ in each subagent-level step.

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

Interactive mode (TUI)

Use Case Example

_No response_

Additional Context

_No response_