Increase the default deployment capacity from 10 to 50

_Migrated from [huimiu/azd-foundry-extension-bugbash#8](https://github.com/huimiu/azd-foundry-extension-bugbash/issues/8), originally reported by @therealjohn._

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This default is low for agents: 

<img width="1002" height="43" alt="Image" src="https://github.com/user-attachments/assets/8523ac07-0fbe-4464-9c52-45ddf6d7ac94" />

Recommend 30-50. 
