feat: add p2p shard swarm

tests/test_tracker_routing.py

@@ -238,6 +238,50 @@ def test_tracker_registration_rejects_invalid_payload():
         tracker.stop()
 
 
+def test_tracker_routes_only_nodes_for_requested_model():
+    """A node registered for one model cannot satisfy another model's route."""
+    tracker = TrackerServer(model_presets={
+        "model-a": {"layers_start": 0, "layers_end": 31},
+        "model-b": {"layers_start": 0, "layers_end": 31},
+    })
+    tracker_port = tracker.start()
+    try:
+        _post_json(
+            f"http://127.0.0.1:{tracker_port}/v1/nodes/register",
+            {"endpoint": "http://127.0.0.1:9001", "shard_start": 0, "shard_end": 31,
+             "model": "model-a", "hardware_profile": {}, "wallet_address": "wallet-a", "score": 1.0},
+        )
+
+        try:
+            _get_json(f"http://127.0.0.1:{tracker_port}/v1/route?model=model-b")
+            raise AssertionError("Expected model-b route to ignore model-a nodes")
+        except urllib.error.HTTPError as exc:
+            assert exc.code == 503
+    finally:
+        tracker.stop()
+
+
+def test_tracker_assignment_coverage_is_model_scoped():
+    """Shard assignment gaps are computed only from nodes serving the same model."""
+    tracker = TrackerServer(model_presets={
+        "model-a": {"layers_start": 0, "layers_end": 31},
+        "model-b": {"layers_start": 0, "layers_end": 31},
+    })
+    tracker_port = tracker.start()
+    try:
+        _post_json(
+            f"http://127.0.0.1:{tracker_port}/v1/nodes/register",
+            {"endpoint": "http://127.0.0.1:9001", "shard_start": 0, "shard_end": 15,
+             "model": "model-a", "hardware_profile": {}, "wallet_address": "wallet-a", "score": 1.0},
+        )
+
+        assignment = _get_json(f"http://127.0.0.1:{tracker_port}/v1/nodes/assign?model=model-b&device=cpu")
+        assert assignment["shard_start"] == 0
+        assert assignment["shard_end"] == 15
+    finally:
+        tracker.stop()
+
+
 def test_tracker_excludes_banned_wallets_from_routes():
     """Tracker refuses route candidates whose wallet is banned on-chain."""
     contracts = LocalSolanaContracts()