Closes #59143

This hides a bunch of actions from the terminal context menu when
showing it in the agent panel.

For agent terminal threads:

<img width="383" height="205" alt="image"
src="https://github.com/user-attachments/assets/a090d62c-7f49-4169-8d82-5cf9577c7444"
/>

For terminals inside of an ACP agent:

<img width="418" height="366" alt="image"
src="https://github.com/user-attachments/assets/225cf0c7-ab28-4a71-b692-b4b89bc074c2"
/>

Previously we would show all of these options both cases:

<img width="221" height="291" alt="image"
src="https://github.com/user-attachments/assets/bcb4e6b6-4a23-48b2-a778-fca4877d2b78"
/>

Also makes the inline assistant actually work inside of terminal threads


Release Notes:

- agent: Fixed an issue where some actions would be displayed in
terminals that would not work