fix: harden port listener detection

src/infra/ports-inspect.test.ts

@@ -0,0 +1,35 @@
+import net from "node:net";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const runCommandWithTimeoutMock = vi.fn();
+
+vi.mock("../process/exec.js", () => ({
+  runCommandWithTimeout: (...args: unknown[]) => runCommandWithTimeoutMock(...args),
+}));
+
+const describeUnix = process.platform === "win32" ? describe.skip : describe;
+
+describeUnix("inspectPortUsage", () => {
+  beforeEach(() => {
+    runCommandWithTimeoutMock.mockReset();
+  });
+
+  it("reports busy when lsof is missing but loopback listener exists", async () => {
+    const server = net.createServer();
+    await new Promise<void>((resolve) => server.listen(0, "127.0.0.1", resolve));
+    const port = (server.address() as net.AddressInfo).port;
+
+    runCommandWithTimeoutMock.mockRejectedValueOnce(
+      Object.assign(new Error("spawn lsof ENOENT"), { code: "ENOENT" }),
+    );
+
+    try {
+      const { inspectPortUsage } = await import("./ports-inspect.js");
+      const result = await inspectPortUsage(port);
+      expect(result.status).toBe("busy");
+      expect(result.errors?.some((err) => err.includes("ENOENT"))).toBe(true);
+    } finally {
+      server.close();
+    }
+  });
+});