fix: resolve file:/// URL validation in simple-resource server

Use typing.cast to bypass AnyUrl host requirement and let types.Resource model handle validation with UrlConstraints(host_required=False).

Fixes #892

Author: nandsha

examples/servers/simple-resource/mcp_simple_resource/server.py

@@ -1,3 +1,5 @@
+from typing import cast
+
 import anyio
 import click
 import mcp.types as types
@@ -26,7 +28,7 @@ def main(port: int, transport: str) -> int:
     async def list_resources() -> list[types.Resource]:
         return [
             types.Resource(
-                uri=AnyUrl(f"file:///{name}.txt"),
+                uri=cast(AnyUrl, f"file:///{name}.txt"),
                 name=name,
                 description=f"A sample text resource named {name}",
                 mimeType="text/plain",