fix: update PromptArgsRawShape for zod v4 type system

Replace generic ZodType<string, ZodTypeDef, string> with concrete ZodString type.
This fixes compatibility with Zod v4's internal type system changes.

Resolves 8 compilation errors (Category D & F):
- 5 errors in mcp.ts type constraints
- 3 cascading errors in example servers

Author: felixweinberger

src/server/mcp.ts

@@ -1133,7 +1133,7 @@ export type RegisteredResourceTemplate = {
 };
 
 type PromptArgsRawShape = {
-    [k: string]: ZodType<string, ZodTypeDef, string> | ZodOptional<ZodType<string, ZodTypeDef, string>>;
+    [k: string]: ZodString | ZodOptional<ZodString>;
 };
 
 export type PromptCallback<Args extends undefined | PromptArgsRawShape = undefined> = Args extends PromptArgsRawShape