feat: let admins manage model placement

tests/test_dynamic_routing.py

@@ -355,6 +355,39 @@ def test_admin_model_load_request_queues_directive_on_joined_node():
     assert heartbeat["directives"][0]["model"] == "Qwen/Qwen2.5-0.5B-Instruct"
 
 
+def test_admin_can_replace_a_served_model_and_release_it():
+    "Forced admin placement replaces a served shard; release queues DROP_SHARD."
+    tracker = TrackerServer(enable_billing=False, validator_service_token="test-admin")
+    port = tracker.start()
+    try:
+        node = _post_json(
+            f"http://127.0.0.1:{port}/v1/nodes/register",
+            {"endpoint": "http://127.0.0.1:9912", "model": "stub-model",
+             "shard_start": 0, "shard_end": 3, "managed_assignment": True,
+             "max_loaded_shards": 1, "memory_mb": 1,
+             "hardware_profile": {"host_id": "full-host"}},
+        )
+        headers = {"Content-Type": "application/json", "Authorization": "Bearer test-admin"}
+        load = urllib.request.Request(
+            f"http://127.0.0.1:{port}/v1/models/load",
+            data=json.dumps({"model": "qwen2.5-0.5b-instruct", "force": True}).encode(),
+            headers=headers, method="POST")
+        with urllib.request.urlopen(load) as response:
+            assert json.loads(response.read())["assignment"]["node_id"] == node["node_id"]
+        heartbeat = _post_json(f"http://127.0.0.1:{port}/v1/nodes/{node['node_id']}/heartbeat", {})
+        assert heartbeat["directives"][0]["action"] == "LOAD_SHARD"
+        release = urllib.request.Request(
+            f"http://127.0.0.1:{port}/v1/models/release",
+            data=json.dumps({"model": "qwen2.5-0.5b-instruct"}).encode(), headers=headers, method="POST")
+        with urllib.request.urlopen(release) as response:
+            assert json.loads(response.read())["released"] == 1
+        heartbeat = _post_json(f"http://127.0.0.1:{port}/v1/nodes/{node['node_id']}/heartbeat", {})
+    finally:
+        tracker.stop()
+
+    assert heartbeat["directives"][0]["action"] == "DROP_SHARD"
+
+
 def test_endpoint_key_distinguishes_same_port_different_hosts():
     "Endpoint key distinguishes same port different hosts\n\nTags: http, performance, routing, tracker"
     from meshnet_node.torch_server import _clamp_downstream_hops, _endpoint_key