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/jobnet-search/cli/src/helpers.ts

@@ -1,4 +1,5 @@
 export const BASE_URL = "https://jobnet.dk/bff"
+export const USER_AGENT = "Mozilla/5.0 (compatible; jobnet-cli/1.0)"
 
 export async function apiFetch<T>(path: string, params?: Record<string, string>): Promise<T> {
   let url = `${BASE_URL}${path}`
@@ -12,6 +13,7 @@ export async function apiFetch<T>(path: string, params?: Record<string, string>)
   for (let attempt = 0; attempt <= maxRetries; attempt++) {
     const response = await fetch(url, {
       headers: {
+        "User-Agent": USER_AGENT,
         "x-csrf": "1",
       },
       signal: AbortSignal.timeout(15000),