feat(provider): add GitHub Enterprise support for Copilot (#2522)

Co-authored-by: Jon-Mikkel Korsvik <48263282+jkorsvik@users.noreply.github.com>
Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: Aiden Cline <aidenpcline@gmail.com>

packages/opencode/src/config/config.ts

@@ -574,6 +574,7 @@ export namespace Config {
                 .object({
                   apiKey: z.string().optional(),
                   baseURL: z.string().optional(),
+                  enterpriseUrl: z.string().optional().describe("GitHub Enterprise URL for copilot authentication"),
                   timeout: z
                     .union([
                       z