Phase 3: Make JSClosure inherit from JSObject for consistency

Co-authored-by: kateinoigakukun <11702759+kateinoigakukun@users.noreply.github.com>

Author: Copilot

Sources/JavaScriptKit/FundamentalObjects/JSClosure.swift

@@ -103,7 +103,7 @@ public class JSOneshotClosure: JSObject, JSClosureProtocol {
 /// button.removeEventListener!("click", JSValue.function(eventListener))
 /// ```
 ///
-public class JSClosure: JSFunction, JSClosureProtocol {
+public class JSClosure: JSObject, JSClosureProtocol {
 
     class SharedJSClosure {
         // Note: 6.0 compilers built with assertions enabled crash when calling
@@ -165,6 +165,10 @@ public class JSClosure: JSFunction, JSClosureProtocol {
         fatalError("JSClosure does not support dictionary literal initialization")
     }
 
+    override public var jsValue: JSValue {
+        .function(JSFunction(id: self.id))
+    }
+
     #if compiler(>=5.5) && (!hasFeature(Embedded) || os(WASI))
     /// Creates a new `JSClosure` that calls the given Swift function asynchronously.
     ///