fix(digitalocean): OAuth flow fails because MAK creation endpoint is retired #28899

Description

DigitalOcean's /v2/gen-ai/models/api_keys endpoint is retired and returns 410. The OAuth flow in the DigitalOcean plugin calls this endpoint to create a Model Access Key after sign-in, so authentication always fails for new users.

DigitalOcean now uses unified API tokens with inference:query scope — the OAuth token itself can be used directly for inference calls without creating a MAK.

Steps to reproduce

1. Run /connect in OpenCode
2. Select DigitalOcean → Login with DigitalOcean
3. Complete browser sign-in
4. Authentication fails with a 410 error