[feature]: GitHub Enterprise Copilot Quota

[buzzcz]

Pre-flight checks

• I searched existing issues and did not find a duplicate request.
• I reviewed current behavior on the production released OpenCode version.

OpenCode version reviewed

1.15.10

Problem statement

I have a Copilot setup in OpenCode from GitHub Enterprise server (GHE). The models work well but the quota is not working.

Proposed change

Add GHE (xyz.ghe.com) as a possibility for Copilot quota - now only GitHub is available.

Alternatives considered

No response

Acceptance criteria

• GHE Copilot quota can be shown