chore: Enforce consistent type imports via @typescript-eslint/consistent-type-imports (#2545)

tests/utils/thumbnail.test.ts

@@ -1,5 +1,5 @@
 import { Task } from '@lit-labs/task';
-import { ReactiveControllerHost } from '@lit/reactive-element';
+import type { ReactiveControllerHost } from '@lit/reactive-element';
 import { afterEach, assert, describe, expect, it, vi } from 'vitest';
 import { mock } from 'vitest-mock-extended';