fix(github-copilot): Grok models get endpoint error due to defaulting to generic OpenAI SDK

Problem

GitHub Copilot Grok models (e.g. copilot-grok-4.6) get an "endpoint error" when used through the opencode CLI. The models are resolved from models.opencode.ai and inherit the generic @ai-sdk/openai-compatible SDK via the GitHub Copilot provider-level npm field, instead of the custom @ai-sdk/github-copilot SDK.

The custom SDK is required to send requests with the correct URL path, headers, and error handling for the GitHub Copilot API.

Root Cause

In fromModelsDevModel() at packages/opencode/src/provider/provider.ts, the npm fallback chain resolves provider.npm ?? "@ai-sdk/openai-compatible". For the github-copilot provider, provider.npm is "@ai-sdk/openai-compatible" (truthy), so the custom @ai-sdk/github-copilot SDK is never selected.

Fix

Three targeted changes:

1. provider.ts (2 locations) — Override the npm to @ai-sdk/github-copilot for github-copilot provider, before falling back to provider.npm. Both the catalog path (fromModelsDevModel) and the config-defined model path (apiNpm assignment) are covered.

2. model.ts:fromCatalogModel — Allow @ai-sdk/github-copilot package through the same OpenAICompatibleChat.route that @ai-sdk/openai-compatible uses.

3. model.ts:supported — Include @ai-sdk/github-copilot alongside @ai-sdk/openai-compatible in the support check.

Files Changed

• packages/opencode/src/provider/provider.ts (2 hunks: fromModelsDevModel + config path)
• packages/core/src/session/runner/model.ts (2 hunks: fromCatalogModel + supported)