fix: reserve and persist background jobs

tests/test_job_registry.py

@@ -0,0 +1,53 @@
+import threading
+
+from dashboard.jobs import JobRegistry
+
+
+def test_job_registry_atomically_reserves_only_one_job_per_kind(tmp_path):
+    registry = JobRegistry(tmp_path / "jobs.json")
+    barrier = threading.Barrier(10)
+    results = []
+
+    def reserve():
+        barrier.wait()
+        results.append(registry.reserve("refresh", details={"full": False}))
+
+    threads = [threading.Thread(target=reserve) for _ in range(10)]
+    for thread in threads:
+        thread.start()
+    for thread in threads:
+        thread.join()
+
+    reserved = [job for job in results if job is not None]
+    assert len(reserved) == 1
+    assert reserved[0]["id"]
+    assert reserved[0]["status"] == "queued"
+    assert registry.active("refresh")["id"] == reserved[0]["id"]
+
+
+def test_job_registry_tracks_completion_and_result(tmp_path):
+    registry = JobRegistry(tmp_path / "jobs.json")
+    job = registry.reserve("history")
+
+    result = registry.run(job["id"], lambda: {"records": 42})
+
+    assert result == {"records": 42}
+    saved = registry.get(job["id"])
+    assert saved["status"] == "complete"
+    assert saved["result"] == {"records": 42}
+    assert saved["started_at"]
+    assert saved["finished_at"]
+    assert registry.active("history") is None
+
+
+def test_job_registry_marks_abandoned_active_jobs_interrupted_on_restart(tmp_path):
+    path = tmp_path / "jobs.json"
+    first = JobRegistry(path)
+    job = first.reserve("refresh")
+
+    restarted = JobRegistry(path)
+
+    recovered = restarted.get(job["id"])
+    assert recovered["status"] == "interrupted"
+    assert recovered["finished_at"]
+    assert restarted.active("refresh") is None