Test Plan: Subagent costs on hover

[pwang347]

• anyOS
• anyOS
• anyOS

Complexity: 3

Author: @pwang347

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Test Cases

• Run multiple subagents at the same time with different models, make sure that the model ID and credits used are correct. (Compare with amount in chat debug view).
• Make sure that the total turn cost is still correct (compare with amount in chat debug view).
• Try different harnesses. This should currently work for Local and Copilot (agent host).