feat(us-016): tracker route for HF models, endpoint dedup, purge logging

Tracker /v1/route now resolves HF model nodes (by hf_repo or short name)
in addition to preset models, using the same greedy interval-cover logic.
This allows distributed inference routing across two nodes each holding
half the model.

Endpoint dedup: re-registering the same endpoint atomically replaces the
old entry so stale registrations don't accumulate across node restarts.

Purge logging: tracker now prints when a node expires due to missed
heartbeats so operators can see dead nodes being removed.

Timing fix: heartbeat timeout raised from 30s to 90s (3 missed beats);
node heartbeat interval lowered from 30s to 20s to maintain margin.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_node_startup.py

@@ -574,6 +574,96 @@ def test_network_assign_gap_found_field():
         tracker.stop()
 
 
+def test_route_finds_hf_model_across_two_nodes():
+    """Tracker /v1/route returns ordered route for HF model even without a preset."""
+    import json as _json
+    import urllib.request as _ur
+
+    tracker = TrackerServer()
+    port = tracker.start()
+    try:
+        def register(endpoint, shard_start, shard_end):
+            data = _json.dumps({
+                "endpoint": endpoint,
+                "model": "Qwen2.5-0.5B-Instruct",
+                "hf_repo": "Qwen/Qwen2.5-0.5B-Instruct",
+                "num_layers": 24,
+                "shard_start": shard_start,
+                "shard_end": shard_end,
+                "hardware_profile": {},
+                "score": 1.0,
+            }).encode()
+            req = _ur.Request(
+                f"http://127.0.0.1:{port}/v1/nodes/register",
+                data=data,
+                headers={"Content-Type": "application/json"},
+                method="POST",
+            )
+            with _ur.urlopen(req) as r:
+                r.read()
+
+        register("http://127.0.0.1:9300", 0, 11)
+        register("http://127.0.0.1:9301", 12, 23)
+
+        # Route by hf_repo (full identifier).
+        resp = _get_json(
+            f"http://127.0.0.1:{port}/v1/route?model=Qwen/Qwen2.5-0.5B-Instruct"
+        )
+        assert resp["route"] == ["http://127.0.0.1:9300", "http://127.0.0.1:9301"]
+
+        # Route also works by short model name.
+        resp2 = _get_json(
+            f"http://127.0.0.1:{port}/v1/route?model=Qwen2.5-0.5B-Instruct"
+        )
+        assert resp2["route"] == ["http://127.0.0.1:9300", "http://127.0.0.1:9301"]
+    finally:
+        tracker.stop()
+
+
+def test_register_deduplicates_same_endpoint():
+    """Re-registering the same endpoint replaces the old entry, not duplicates it."""
+    import json as _json
+    import urllib.request as _ur
+
+    tracker = TrackerServer()
+    port = tracker.start()
+    try:
+        def register(shard_start, shard_end):
+            data = _json.dumps({
+                "endpoint": "http://127.0.0.1:9400",
+                "model": "Qwen2.5-0.5B-Instruct",
+                "hf_repo": "Qwen/Qwen2.5-0.5B-Instruct",
+                "num_layers": 24,
+                "shard_start": shard_start,
+                "shard_end": shard_end,
+                "hardware_profile": {},
+                "score": 1.0,
+            }).encode()
+            req = _ur.Request(
+                f"http://127.0.0.1:{port}/v1/nodes/register",
+                data=data,
+                headers={"Content-Type": "application/json"},
+                method="POST",
+            )
+            with _ur.urlopen(req) as r:
+                return _json.loads(r.read())
+
+        register(0, 23)  # initial full-model registration
+        register(12, 23)  # re-register with corrected shard range
+
+        # After re-register, tracker should see only one node at 12-23 for this endpoint.
+        # If both were still registered, the gap scan would find no gap (0-23 still covers).
+        # With dedup, the old 0-23 is gone and a real gap 0-11 exists.
+        assign_resp = _get_json(
+            f"http://127.0.0.1:{port}/v1/network/assign?device=cpu&vram_mb=0"
+            "&hf_repo=Qwen/Qwen2.5-0.5B-Instruct"
+        )
+        assert assign_resp["gap_found"] is True
+        assert assign_resp["shard_start"] == 0, "old 0-23 entry should have been replaced"
+    finally:
+        tracker.stop()
+
+
 def test_startup_cpu_fallback(tmp_path, monkeypatch):
     """Node starts with CPU warning when no GPU is detected."""
     import meshnet_node.startup as startup_mod