fix(simulation): reserve disk space before artifact import

tests/test_simulation_projects.py

@@ -611,6 +611,63 @@ def test_failed_project_retries_from_retained_source_and_releases_old_job(tmp_pa
     assert queued["source"]["uploaded_byte_length"] == queued["source"]["total_byte_length"]
 
 
+def test_import_evicts_only_worker_backed_archive_staging_when_disk_is_low(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    store = SimulationProjectStore(tmp_path)
+    project = store.create(
+        name="Worker-backed archive",
+        scene_type="outdoor",
+        source_kind="archive",
+        files=[{"logical_path": "scene.rar", "byte_length": 6}],
+    )
+    source_file = project["source"]["files"][0]
+    store.append_upload(
+        project["project_id"],
+        source_file["file_id"],
+        offset=0,
+        payload=b"source",
+    )
+    store.begin_build(project["project_id"])
+    store.update_processing(
+        project["project_id"],
+        status="processing",
+        provider_job_id="gsp-20260826000000-deadbeef",
+        provider_state="ready",
+    )
+    service = SimulationProjectService(store, provider_factory=lambda: None)
+    source_path = store.source_root(project["project_id"]) / "scene.rar"
+
+    class _DiskUsage:
+        def __init__(self, free: int) -> None:
+            self.free = free
+
+    monkeypatch.setattr(
+        "k1link.simulation.projects.shutil.disk_usage",
+        lambda _path: _DiskUsage(0 if source_path.exists() else 10 * 1024**3),
+    )
+    artifacts = [
+        {
+            "role": "preview",
+            "logical_path": "preview.sog",
+            "media_type": "application/octet-stream",
+            "sha256": "a" * 64,
+            "byte_length": 1024,
+        }
+    ]
+
+    service._ensure_import_capacity(
+        project["project_id"],
+        artifacts,
+        store.artifacts_root(project["project_id"]),
+    )
+
+    assert not source_path.exists()
+    retained_metadata = store.get(project["project_id"])["source"]
+    assert retained_metadata["uploaded_byte_length"] == retained_metadata["total_byte_length"]
+
+
 def test_failed_local_project_reattaches_to_live_provider_job_without_rebuild(
     tmp_path: Path,
 ) -> None: