fix(jobbank): parse JobPosting entries nested in JSON-LD @graph (#190)

Extracts the JSON-LD JobPosting lookup into a recursive parseJobPostingJsonLd helper that handles top-level objects, arrays, and @graph wrappers (including nested combinations), keeps skipping malformed scripts, and covers all four cases with network-free Bun tests.

By @luochen211. Closes #189.

.agents/skills/jobbank-search/cli/tests/detail-jsonld.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, test } from "bun:test"
+import { parseJobPostingJsonLd } from "../src/helpers"
+
+const script = (value: string) => `<script type="application/ld+json">${value}</script>`
+
+describe("parseJobPostingJsonLd", () => {
+  test("finds a JobPosting inside an @graph", () => {
+    const html = script(
+      JSON.stringify({
+        "@context": "https://schema.org",
+        "@graph": [
+          { "@type": "WebPage", name: "Jobs" },
+          { "@type": "JobPosting", title: "Data Engineer" },
+        ],
+      }),
+    )
+
+    expect(parseJobPostingJsonLd(html)).toEqual({
+      "@type": "JobPosting",
+      title: "Data Engineer",
+    })
+  })
+
+  test("preserves top-level object and array support", () => {
+    expect(parseJobPostingJsonLd(script('{"@type":"JobPosting","title":"One"}'))?.title).toBe("One")
+    expect(
+      parseJobPostingJsonLd(script('[{"@type":"WebPage"},{"@type":"JobPosting","title":"Two"}]'))?.title,
+    ).toBe("Two")
+  })
+
+  test("skips malformed scripts and checks later JSON-LD", () => {
+    const html = `${script("{not-json")}${script('{"@type":"JobPosting","title":"Valid"}')}`
+
+    expect(parseJobPostingJsonLd(html)?.title).toBe("Valid")
+  })
+
+  test("returns null when no JobPosting exists", () => {
+    expect(parseJobPostingJsonLd(script('{"@graph":[{"@type":"WebPage"}]}'))).toBeNull()
+  })
+})