fix(jobdanmark-search): back off on 429/5xx in detail instead of failing on the first attempt (#460)

`detail` called fetch() directly rather than going through the CLI's own
request wrappers, so it had none of the three things apiFetch/apiPost
guarantee: no 429/5xx retry loop, a hand-inlined User-Agent that would
drift from the exported USER_AGENT, and a timeout no wrapper test covered.
A rate-limited detail page wrote API_ERROR and exited after ONE attempt;
jobnet, jobbank, jobindex, linkedin, and freehire all retry up to six
times on the same response. /scrape calls detail once per shortlisted
posting, so a burst that tripped jobdanmark's limiter dropped those
postings (no description, no deadline) while any other portal rode it out.

Demonstrated by driving the real command handler with a stubbed 429 and
instant timers: 1 fetch attempt and exit 1 before, 7 after (initial try
plus six retries, the contract's schedule).

Add htmlFetch to helpers.ts with the same backoff, timeout, and shared
User-Agent as the JSON wrappers - 404 returns null so detail keeps its
NOT_FOUND contract - and route detail through it. The retry-backoff,
user-agent, and request-timeout suites now cover all three wrappers, and
the new detail-backoff.test.ts exercises the handler path itself; its two
retry cases fail against the bare fetch().

.agents/skills/jobdanmark-search/cli/src/helpers.ts

@@ -64,6 +64,45 @@ export async function apiPost<T>(path: string, body: unknown): Promise<T> {
   throw new Error("API request failed after max retries")
 }
 
+/**
+ * Fetch a rendered jobdanmark.dk page as text, with the same 429/5xx backoff,
+ * request timeout, and User-Agent as apiFetch/apiPost. `detail` reads HTML
+ * rather than the JSON API; it used to call fetch() directly with none of the
+ * three, so a rate-limited detail page failed on the first 429 while every
+ * other portal's detail command retried. Returns null on 404 so the caller
+ * keeps its own NOT_FOUND contract.
+ */
+export async function htmlFetch(url: string): Promise<string | null> {
+  const maxRetries = 6
+  let delay = 500
+  for (let attempt = 0; attempt <= maxRetries; attempt++) {
+    const response = await fetch(url, {
+      headers: {
+        "Accept": "text/html,application/xhtml+xml",
+        "User-Agent": USER_AGENT,
+      },
+      signal: AbortSignal.timeout(15000),
+    })
+    if (response.status === 429 || response.status >= 500) {
+      if (attempt === maxRetries) {
+        throw new Error(`API request failed: ${response.status} ${response.statusText}`)
+      }
+      const jitter = Math.floor(Math.random() * 500)
+      await new Promise((resolve) => setTimeout(resolve, delay + jitter))
+      delay = Math.min(delay * 2, 5000)
+      continue
+    }
+    if (response.status === 404) {
+      return null
+    }
+    if (!response.ok) {
+      throw new Error(`API request failed: ${response.status} ${response.statusText}`)
+    }
+    return response.text()
+  }
+  throw new Error("API request failed after max retries")
+}
+
 export function writeError(error: string, code: string): void {
   process.stderr.write(JSON.stringify({ error, code }) + "\n")
 }