feat(FN-2624): surface task token usage on task cards

- Render a compact token usage indicator in TaskCard footer with accessible labeling and token-aware styling
- Track token usage fields in the TaskCard memo comparator and expose a comparator test helper for regression coverage
- Add TaskCard tests for token usage rendering behavior and comparator invalidation on token usage updates
- Configure runtime plugin Vitest setups with an @fusion/engine source alias for reliable workspace test resolution
- Keep restart integration child_process spawn mocking aligned with execSync-driven merge verification behavior

plugins/fusion-plugin-hermes-runtime/vitest.config.ts

@@ -1,3 +1,4 @@
+import { fileURLToPath } from "node:url";
 import { defineConfig } from "vitest/config";
 
 const requestedMaxWorkers = Number.parseInt(process.env.VITEST_MAX_WORKERS ?? "2", 10);
@@ -5,6 +6,11 @@ const maxWorkers = Math.max(1, Math.min(4, Number.isFinite(requestedMaxWorkers)
 process.env.VITEST_MAX_WORKERS = String(maxWorkers);
 
 export default defineConfig({
+  resolve: {
+    alias: {
+      "@fusion/engine": fileURLToPath(new URL("../../packages/engine/src/index.ts", import.meta.url)),
+    },
+  },
   test: {
     include: ["src/**/*.test.ts"],
     pool: "threads",