refactor(gateway): streamline control-ui secure file serving

src/gateway/control-ui.http.test.ts

@@ -180,6 +180,29 @@ describe("handleControlUiHttpRequest", () => {
     });
   });
 
+  it("serves HEAD for in-root assets without writing a body", async () => {
+    await withControlUiRoot({
+      fn: async (tmp) => {
+        const assetsDir = path.join(tmp, "assets");
+        await fs.mkdir(assetsDir, { recursive: true });
+        await fs.writeFile(path.join(assetsDir, "actual.txt"), "inside-ok\n");
+
+        const { res, end } = makeMockHttpResponse();
+        const handled = handleControlUiHttpRequest(
+          { url: "/assets/actual.txt", method: "HEAD" } as IncomingMessage,
+          res,
+          {
+            root: { kind: "resolved", path: tmp },
+          },
+        );
+
+        expect(handled).toBe(true);
+        expect(res.statusCode).toBe(200);
+        expect(end.mock.calls[0]?.length ?? -1).toBe(0);
+      },
+    });
+  });
+
   it("rejects symlinked SPA fallback index.html outside control-ui root", async () => {
     await withControlUiRoot({
       fn: async (tmp) => {