Implement backend jobs registry and API endpoints for job management

tests/test_jobs_backend.py

@@ -0,0 +1,59 @@
+from jobs_backend import BackendJobs
+
+
+def test_backend_jobs_adopt_progress_and_complete_redacts_raw_payloads():
+    jobs = BackendJobs()
+    jobs.register_provider({
+        "providerId": "provider.test",
+        "pluginId": "plugin_test",
+        "label": "Test Provider",
+        "jobTypes": ["test.convert"],
+        "actions": ["status"],
+    })
+
+    adopted = jobs.adopt(
+        provider_id="provider.test",
+        job_type="test.convert",
+        job_id="backend-1",
+        state="queued",
+        requester_id="plugin_test",
+        safe_label="Convert Example Song",
+        target={"safeRef": "target-abc", "backendJobId": "backend-1"},
+        inputs={"safeFingerprint": "input-abc"},
+    )
+    assert adopted["outcome"] == "handled"
+
+    progressed = jobs.update_progress(
+        "provider.test",
+        "backend-1",
+        {"mode": "determinate", "percent": 42, "step": "convert", "message": "/Users/example/Secret.psarc token=abc"},
+    )
+    assert progressed["outcome"] == "handled"
+
+    completed = jobs.complete("provider.test", "backend-1", {"resultSummary": "Wrote /Users/example/out.sloppak"})
+    assert completed["outcome"] == "completed"
+
+    snapshot = jobs.snapshot()
+    text = str(snapshot)
+    assert "provider.test" in text
+    assert "target-abc" in text
+    assert "Secret.psarc" not in text
+    assert "token=abc" not in text
+    assert "/Users/example" not in text
+    assert snapshot["jobs"]["recentTerminal"][0]["state"] == "completed"
+
+
+def test_backend_jobs_provider_unavailable_settles_active_jobs():
+    jobs = BackendJobs()
+    jobs.register_provider({
+        "providerId": "provider.test",
+        "jobTypes": ["test.convert"],
+    })
+    jobs.adopt(provider_id="provider.test", job_type="test.convert", job_id="backend-2", state="running")
+
+    result = jobs.mark_provider_unavailable("provider.test", "backend stopped")
+    snapshot = jobs.snapshot()
+
+    assert result["outcome"] == "provider-unavailable"
+    assert snapshot["jobs"]["active"] == []
+    assert snapshot["jobs"]["recentTerminal"][0]["state"] == "provider-unavailable"