feat(copilot): fetch and persist user email and display name on login

- Expand OAuth scope to include read:user for full profile access
- Add GitHubUserInfo struct with Login, Email, Name fields
- Update FetchUserInfo to return complete user profile
- Add Email and Name fields to CopilotTokenStorage and CopilotAuthBundle
- Fix provider string bug: 'github' -> 'github-copilot' in auth_files.go
- Fix semantic bug: email field was storing username
- Update Label to prefer email over username in both CLI and Web API paths
- Add 9 unit tests covering new functionality

sdk/auth/github_copilot.go

@@ -86,6 +86,8 @@ func (a GitHubCopilotAuthenticator) Login(ctx context.Context, cfg *config.Confi
 	metadata := map[string]any{
 		"type":         "github-copilot",
 		"username":     authBundle.Username,
+		"email":        authBundle.Email,
+		"name":         authBundle.Name,
 		"access_token": authBundle.TokenData.AccessToken,
 		"token_type":   authBundle.TokenData.TokenType,
 		"scope":        authBundle.TokenData.Scope,
@@ -98,13 +100,18 @@ func (a GitHubCopilotAuthenticator) Login(ctx context.Context, cfg *config.Confi
 
 	fileName := fmt.Sprintf("github-copilot-%s.json", authBundle.Username)
 
+	label := authBundle.Email
+	if label == "" {
+		label = authBundle.Username
+	}
+
 	fmt.Printf("\nGitHub Copilot authentication successful for user: %s\n", authBundle.Username)
 
 	return &coreauth.Auth{
 		ID:       fileName,
 		Provider: a.Provider(),
 		FileName: fileName,
-		Label:    authBundle.Username,
+		Label:    label,
 		Storage:  tokenStorage,
 		Metadata: metadata,
 	}, nil