fix(portal-clis): emit the contract's id field from jobnet and jobdanmark search results (#518)

/add-portal's contract says every search result carries at least id,
title, company, location, date, url, and the four other shipped CLIs
emit id. When #340 added the company/location/date/url aliases to these
two, id was left out: jobnet exposed the value only as jobAdId,
jobdanmark only as slug, so a consumer reading every portal's JSON
through one shape had to special-case both to call detail.

Purely additive: id equals jobAdId on jobnet and slug on jobdanmark, the
native keys stay, nothing is renamed. Each SKILL.md notes the alias. The
additive-contract test in each CLI now asserts id and its equality with
the native key; both fail on master.

.agents/skills/jobdanmark-search/cli/tests/search-normalization.test.ts

@@ -20,16 +20,19 @@ function item(): ApiSearchItem {
 }
 
 describe("Jobdanmark search normalization", () => {
-  test("additively emits the /scrape contract fields (company, location, date, deadline)", () => {
+  test("additively emits the /scrape contract fields (id, company, location, date, deadline, url)", () => {
     const result = normalizeItem(item());
 
     expect(result).toMatchObject({
+      id: "softwareudvikler-til-statens-it",
       company: "Statens It",
       location: "Ballerup",
       date: "2026-07-27",
       deadline: "2026-08-17",
       url: "https://jobdanmark.dk/job/softwareudvikler-til-statens-it",
     });
+    // `id` is the contract name for the value `detail <slug>` consumes.
+    expect(result.id).toBe(result.slug);
   });
 
   test("maps a missing address zip and a null deadline to null", () => {