Preserve authentication cancellation at the response limit

internal/llm/openrouter_authentication.go

@@ -59,6 +59,9 @@ func (c *OpenAICompatibleClient) ProbeOpenRouterKey(ctx context.Context, endpoin
 			return result, nil
 		}
 		contents, err := io.ReadAll(io.LimitReader(response.Body, maxAuthenticationResponseBytes+1))
+		if err != nil && ctx.Err() != nil {
+			return result, ctx.Err()
+		}
 		if len(contents) > maxAuthenticationResponseBytes {
 			result.Overflow = true
 			return result, nil