Fix URI template derivation and lookup (#530)

* Use lowercase host in resource URI template derivation.

* Address feedback

* Add casing testing for non-templated resource lookups.

* Fix uri primitive lookup

* Use a hardcoded mcp hostname in derived resource template URIs and ensure built-in resources work with the VS Code client.

* Address feedback

* Fix equality comparison

* Use dedicated type for resource collections.

src/ModelContextProtocol.Core/Protocol/ResourcesCapability.cs

@@ -103,5 +103,5 @@ public sealed class ResourcesCapability
     /// </para>
     /// </remarks>
     [JsonIgnore]
-    public McpServerPrimitiveCollection<McpServerResource>? ResourceCollection { get; set; }
+    public McpServerResourceCollection? ResourceCollection { get; set; }
 }