feat(cli): identify jobnet and jobdanmark API requests with an honest User-Agent (#283)

* fix(cli): send User-Agent on jobnet and jobdanmark API requests

apiFetch/apiPost hit the portals' APIs without a User-Agent header, while every other Danish-portal CLI sends one on purpose (jobbank exports USER_AGENT and its tests assert it; jobindex sets it on htmlFetch). Requests without one are rejected by the portals' bot filters.

* fix(cli): satisfy strict typecheck in user-agent regression test

* refactor(cli): reframe user-agent tests as honest self-identification

* docs(changelog): entry for #283 user-agent self-identification

.agents/skills/jobdanmark-search/cli/tests/user-agent.test.ts

@@ -0,0 +1,48 @@
+import { afterEach, describe, expect, test } from "bun:test";
+import { apiFetch, apiPost, USER_AGENT } from "../src/helpers";
+
+// Bun's fetch injects an anonymous default User-Agent (Bun/1.3.10) when code
+// sets none. This CLI should say who is asking, in the honest style jobindex
+// already uses on htmlFetch ("Mozilla/5.0 (compatible; jobindex-cli/1.0)").
+// Assert the header is present on every request. Fails on the pre-change code.
+const originalFetch = globalThis.fetch;
+afterEach(() => {
+  globalThis.fetch = originalFetch;
+});
+
+function headerValue(headers: RequestInit["headers"], name: string): string | null {
+  if (headers instanceof Headers) return headers.get(name);
+  if (Array.isArray(headers)) {
+    const found = headers.find(([k]) => k === name);
+    return found ? String(found[1]) : null;
+  }
+  const value = headers?.[name];
+  return typeof value === "string" ? value : null;
+}
+
+describe("apiFetch user agent", () => {
+  test("sends a User-Agent header", async () => {
+    let init: RequestInit | undefined;
+    globalThis.fetch = (async (_url: string | URL | Request, i?: RequestInit) => {
+      init = i;
+      return new Response("{}", { status: 200 });
+    }) as unknown as typeof fetch;
+
+    await apiFetch("/api/search/autocomplete", { q: "it" });
+    expect(headerValue(init?.headers, "User-Agent")).toBe(USER_AGENT);
+  });
+});
+
+describe("apiPost user agent", () => {
+  test("sends a User-Agent header alongside Content-Type", async () => {
+    let init: RequestInit | undefined;
+    globalThis.fetch = (async (_url: string | URL | Request, i?: RequestInit) => {
+      init = i;
+      return new Response("{}", { status: 200 });
+    }) as unknown as typeof fetch;
+
+    await apiPost("/api/jobsearch/search/1", { q: "it" });
+    expect(headerValue(init?.headers, "User-Agent")).toBe(USER_AGENT);
+    expect(headerValue(init?.headers, "Content-Type")).toBe("application/json");
+  });
+});