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/jobnet-search/cli/tests/search-normalization.test.ts

@@ -128,11 +128,12 @@ describe("Jobnet search normalization", () => {
     expect("description" in output.results[0]).toBe(false);
   });
 
-  test("additively emits the /scrape contract fields (company, location, date, deadline, url)", () => {
+  test("additively emits the /scrape contract fields (id, company, location, date, deadline, url)", () => {
     const output = createSearchOutput(apiResponse(), { ...flags, limit: undefined });
 
     expect(output.results).toHaveLength(2);
     expect(output.results[0]).toMatchObject({
+      id: "job-1",
       company: "Acme",
       location: null,
       date: "2026-07-01",
@@ -140,6 +141,7 @@ describe("Jobnet search normalization", () => {
       url: "https://jobnet.dk/find-job/job-1",
     });
     expect(output.results[1]).toMatchObject({
+      id: "job-2",
       company: "Example Co",
       location: "København Ø",
       date: "2026-07-02",
@@ -148,6 +150,8 @@ describe("Jobnet search normalization", () => {
     });
     expect(output.results[0].hiringOrgName).toBe("Acme");
     expect(output.results[1].applicationDeadline).toBe("2026-08-01T23:59:00+02:00");
+    // `id` is the contract name for the value `detail <jobAdId>` consumes.
+    expect(output.results[0].id).toBe(output.results[0].jobAdId);
   });
 
   test("maps Jobnet's undisclosed-deadline sentinel (1900-01-01) to null", () => {