fix(login): delete OAuth token using the stored login name

- Pass the stored login name to DeleteOAuthToken instead of the
  CLI-provided one: the login lookup is case-insensitive but credstore
  keys are exact-match, so deleting with different casing left the
  encrypted token orphaned in the credential store

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

modules/config/login.go

@@ -240,11 +240,14 @@ func DeleteLogin(name string) error {
 		}
 
 		isOAuth := config.Logins[idx].IsOAuth()
+		// Use the stored login name, not the CLI-provided one: the lookup above
+		// is case-insensitive, but credstore keys are exact-match.
+		storedName := config.Logins[idx].Name
 		config.Logins = append(config.Logins[:idx], config.Logins[idx+1:]...)
 
 		// Clean up credstore tokens for OAuth logins
 		if isOAuth {
-			_ = DeleteOAuthToken(name)
+			_ = DeleteOAuthToken(storedName)
 		}
 
 		return saveConfigUnsafe()