fix(canvas/test): add missing FilesToolbar import + renderToolbar helper

PR #881 rewrote FilesTab.test.tsx and deleted renderToolbar(), but
left one orphaned test inside the "upload guard" block that called it.
Adds the import + helper so the focus-visible accessibility test runs.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

canvas/src/components/tabs/FilesTab/__tests__/FilesTab.test.tsx

@@ -11,6 +11,7 @@ import { afterEach, describe, expect, it, vi } from "vitest";
 import { cleanup, fireEvent, render, screen, waitFor } from "@testing-library/react";
 import React from "react";
 
+import { FilesToolbar } from "../FilesToolbar";
 import { FilesTab } from "../../FilesTab.tsx";
 import type { FileEntry } from "../../FilesTab/tree";
 
@@ -30,6 +31,24 @@ afterEach(() => {
 
 const emptyFileList: FileEntry[] = [];
 
+/** Render FilesToolbar directly — used by the focus-visible accessibility test. */
+function renderToolbar(props: Partial<React.ComponentProps<typeof FilesToolbar>> = {}) {
+  const noop = vi.fn();
+  return render(
+    <FilesToolbar
+      root="/configs"
+      setRoot={noop}
+      fileCount={0}
+      onNewFile={noop}
+      onUpload={noop}
+      onDownloadAll={noop}
+      onClearAll={noop}
+      onRefresh={noop}
+      {...props}
+    />,
+  );
+}
+
 /** Render FilesTab with a non-external runtime (triggers PlatformOwnedFilesTab). */
 function renderPlatformTab(extraProps: Partial<React.ComponentProps<typeof FilesTab>> = {}) {
   return render(