filter webview editors out of 'add context'

[eleanorjboyd]

Steps to Reproduce:

1. open a PR view
2. go to the attach menu, try and select the PR, get an errored attachment

Screen.Recording.2025-07-11.at.9.38.56.AM.mov

[alexr00]

@roblourens and @mjbvz is there something extensions with webviews should be doing here, or is this not supported?

[roblourens]

Is this just attached as a file or are you doing something special already? It wouldn't work as a file but I'm not sure why it didn't get filtered out of the attach picker, thought we did that

[eleanorjboyd]

I didn't do anything special just opened the PR view. idk if you were asking me or alex

[alexr00]

@roblourens it's just listed in the picker when you click the "Add Context" button in the Chat input.