refactor: extract CompletableSchema type for clarity

Extracts the intersection type to a named CompletableSchema<T> type alias,
making the function signature more readable and reusable.

Author: felixweinberger

src/server/completable.ts

@@ -17,6 +17,11 @@ export interface CompletableDef<T extends ZodTypeAny = ZodTypeAny> {
     typeName: McpZodTypeKind.Completable;
 }
 
+/**
+ * A Zod schema that has been wrapped with completion capabilities.
+ */
+export type CompletableSchema<T extends ZodTypeAny> = T & { _def: T['_def'] & CompletableDef<T> };
+
 /**
  * Wraps a Zod type to provide autocompletion capabilities. Useful for, e.g., prompt arguments in MCP.
  *
@@ -26,7 +31,7 @@ export interface CompletableDef<T extends ZodTypeAny = ZodTypeAny> {
 export function completable<T extends ZodTypeAny>(
     schema: T,
     complete: CompleteCallback<T>
-): T & { _def: T['_def'] & CompletableDef<T> } {
+): CompletableSchema<T> {
     // Create new schema object inheriting from original
     const wrapped = Object.create(Object.getPrototypeOf(schema));
 
@@ -62,5 +67,5 @@ export function completable<T extends ZodTypeAny>(
         def: newDef
     };
 
-    return wrapped as T & { _def: T['_def'] & CompletableDef<T> };
+    return wrapped as CompletableSchema<T>;
 }