[FEATURE]: Add Gab.AI

[rma92]

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

Add Gab.AI as a provider in OpenCode. The provider appears when GAB_API_KEY is set.

This gives users access to evaluate many different models through a single Gab account, which is useful for comparing models without managing multiple provider accounts.

[github-actions]

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

• [FEATURE]:Add Support for Gab.ai API Provider #8762: Same request — Add Support for Gab.ai API Provider (closed)

[hyder365]

This would be great to have.