feat: model registry with virtual-to-physical resolution

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

kischdle/llmux/llmux/model_registry.py

@@ -0,0 +1,36 @@
+from llmux.config import PhysicalModel, VirtualModel, load_models_config
+
+
+class ModelRegistry:
+    def __init__(
+        self,
+        physical: dict[str, PhysicalModel],
+        virtual: dict[str, VirtualModel],
+    ):
+        self._physical = physical
+        self._virtual = virtual
+
+    @classmethod
+    def from_config(cls) -> "ModelRegistry":
+        physical, virtual = load_models_config()
+        return cls(physical, virtual)
+
+    def list_virtual_models(self) -> list[dict]:
+        return [
+            {
+                "id": name,
+                "object": "model",
+                "created": 0,
+                "owned_by": "llmux",
+            }
+            for name in self._virtual
+        ]
+
+    def resolve(self, virtual_name: str) -> tuple[str, PhysicalModel, dict]:
+        """Resolve a virtual model name to (physical_id, PhysicalModel, params)."""
+        vm = self._virtual[virtual_name]  # raises KeyError if unknown
+        pm = self._physical[vm.physical]
+        return vm.physical, pm, dict(vm.params)
+
+    def get_physical(self, physical_id: str) -> PhysicalModel:
+        return self._physical[physical_id]  # raises KeyError if unknown