feat(FN-2663): add cached update-check setting, APIs, and banner

- Add global updateCheckEnabled setting to core schema/types and wire dashboard command to cache update checks in the CLI
- Implement dashboard server update-check cache module plus REST routes for status and refresh behavior
- Add dashboard client hook, legacy API helpers, and UpdateAvailableBanner UI to show cached CLI update notices
- Cover update-check server routes, hook behavior, banner rendering, and route registration with focused tests
- Document update-check configuration and API behavior in architecture and settings reference docs

packages/dashboard/src/routes/register-update-check-routes.ts

@@ -0,0 +1,61 @@
+import { readFileSync } from "node:fs";
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
+import { resolveGlobalDir } from "@fusion/core";
+import { clearUpdateCheckCache, performUpdateCheck } from "../update-check.js";
+import type { ApiRouteRegistrar } from "./types.js";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+const CLI_PACKAGE_VERSION = (() => {
+  try {
+    const packageJsonPath = join(__dirname, "..", "..", "..", "cli", "package.json");
+    const packageJson = JSON.parse(readFileSync(packageJsonPath, "utf-8")) as {
+      version?: unknown;
+    };
+
+    if (typeof packageJson.version === "string" && packageJson.version.length > 0) {
+      return packageJson.version;
+    }
+  } catch {
+    // Fall through to env/default fallback.
+  }
+
+  return process.env.npm_package_version ?? "0.0.0";
+})();
+
+export const registerUpdateCheckRoutes: ApiRouteRegistrar = (ctx) => {
+  const { router, store, rethrowAsApiError } = ctx;
+
+  router.get("/update-check", async (_req, res) => {
+    try {
+      const globalSettings = await store.getGlobalSettingsStore().getSettings();
+      if (globalSettings.updateCheckEnabled === false) {
+        res.json({
+          updateAvailable: false,
+          disabled: true,
+          currentVersion: CLI_PACKAGE_VERSION,
+          latestVersion: null,
+          lastChecked: Date.now(),
+        });
+        return;
+      }
+
+      const result = await performUpdateCheck(resolveGlobalDir(), CLI_PACKAGE_VERSION);
+      res.json(result);
+    } catch (error) {
+      rethrowAsApiError(error, "Failed to perform update check");
+    }
+  });
+
+  router.post("/update-check/refresh", async (_req, res) => {
+    try {
+      const fusionDir = resolveGlobalDir();
+      await clearUpdateCheckCache(fusionDir);
+      const result = await performUpdateCheck(fusionDir, CLI_PACKAGE_VERSION);
+      res.json(result);
+    } catch (error) {
+      rethrowAsApiError(error, "Failed to refresh update check");
+    }
+  });
+};