feat: add UnsupportedCapabilityError and update ErrorCode enum

Author: matteo-gobbo

packages/core/src/types/types.ts

@@ -238,7 +238,8 @@ export enum ErrorCode {
     InternalError = -32603,
 
     // MCP-specific error codes
-    UrlElicitationRequired = -32042
+    UrlElicitationRequired = -32042,
+    UnsupportedCapability = -32043 
 }
 
 /**
@@ -2369,6 +2370,12 @@ export class UrlElicitationRequiredError extends McpError {
     }
 }
 
+export class UnsupportedCapabilityError extends McpError {
+    constructor(message: string) {
+        super(ErrorCode.UnsupportedCapability, message);
+    }
+}
+
 type Primitive = string | number | boolean | bigint | null | undefined;
 type Flatten<T> = T extends Primitive
     ? T