[FEATURE]: support openrouter stealth models

[modpotato]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

its very possible im doing this wrong, but the model list/selector inside opencode doesnt try to check the actual openrouter /models endpoint. is there any reason for this? if not it would probably make stealth models work out of the box..

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• No endpoints found error from Openrouter -> Should be able to re-fetch/update model list #10594: No endpoints found error from Openrouter -> Should be able to re-fetch/update model list

Feel free to ignore if none of these address your specific case.

[modpotato]

ic i should put this on models.dev, sorry!