fix(schemas): one definition of the capabilities payload

GET /computes/{id} answered with only part of the capabilities the compute
reports: the response schema kept a second, private Capabilities class of
its own (it knew ubridge_tc and nothing else), and FastAPI's response model
silently drops fields it does not define — so ubridge_tap and
ubridge_iol_tap never reached clients even though the compute had sent
them and links were already being built on those datapaths.

Import the one definition instead of duplicating it, so the next capability
cannot drift the same way.

tests/api/routes/controller/test_computes.py

@@ -74,6 +74,40 @@ class TestComputeRoutes:
         assert response.status_code == status.HTTP_200_OK
         assert response.json()["compute_id"] == str(test_compute.compute_id)
 
+    async def test_compute_get_reports_every_capability(self, app: FastAPI, client: AsyncClient, controller) -> None:
+        """
+        The capabilities payload the compute reports must survive the
+        response model intact. The local compute is the interesting one: it
+        is the controller object serialized straight through, and a second,
+        private Capabilities definition in the response schema silently
+        stripped the kernel-datapath fields (ubridge_tap, ubridge_iol_tap)
+        there — links were then built on a datapath clients could not see.
+        """
+
+        await controller.add_compute(
+            compute_id="local", name="local", host="127.0.0.1", port=3080, force=True, connect=False
+        )
+        controller.get_compute("local")._capabilities.update(
+            {
+                "version": "3.1.0",
+                "node_types": ["docker"],
+                "platform": "linux",
+                "cpus": 4,
+                "memory": 1024,
+                "disk_size": 2048,
+                "ubridge_tc": {"netem": ["delay"], "ebpf": True, "ebpf_modes": ["nth"], "cbpf": True},
+                "ubridge_tap": True,
+                "ubridge_iol_tap": False,
+            }
+        )
+
+        response = await client.get(app.url_path_for("get_compute", compute_id="local"))
+        assert response.status_code == status.HTTP_200_OK
+        capabilities = response.json()["capabilities"]
+        assert capabilities["ubridge_tap"] is True
+        assert capabilities["ubridge_iol_tap"] is False
+        assert capabilities["ubridge_tc"]["netem"] == ["delay"]
+
     async def test_compute_get_local(self, app: FastAPI, client: AsyncClient, controller) -> None:
 
         await controller.add_compute(