fix: support github-copilot provider in AccountInfo logging

Changed the provider matching logic in AccountInfo() method to use
prefix matching instead of exact matching. This allows both 'github'
(Kiro OAuth) and 'github-copilot' providers to be correctly identified
as OAuth providers, enabling proper debug logging output.

Before: Use OAuth logs were missing for github-copilot requests
After: Logs show "Use OAuth provider=github-copilot auth_file=..."

Co-Authored-By: Claude (claude-sonnet-4.5) <noreply@anthropic.com>

sdk/cliproxy/auth/types.go

@@ -227,8 +227,8 @@ func (a *Auth) AccountInfo() (string, string) {
 		}
 	}
 
-	// For GitHub provider, return username
-	if strings.ToLower(a.Provider) == "github" {
+	// For GitHub provider (including github-copilot), return username
+	if strings.HasPrefix(strings.ToLower(a.Provider), "github") {
 		if a.Metadata != nil {
 			if username, ok := a.Metadata["username"].(string); ok {
 				username = strings.TrimSpace(username)