Phase 2: Unify JSValue representation - functions now use .object case

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

Author: Copilot

Sources/JavaScriptKit/ConvertibleToJSValue.swift

@@ -209,7 +209,7 @@ extension RawJSValue: ConvertibleToJSValue {
         case .undefined:
             return .undefined
         case .function:
-            return .function(JSFunction(id: UInt32(payload1)))
+            return .object(JSFunction(id: UInt32(payload1)))
         case .symbol:
             return .symbol(JSSymbol(id: UInt32(payload1)))
         case .bigInt:

Sources/JavaScriptKit/FundamentalObjects/JSClosure.swift

@@ -166,7 +166,7 @@ public class JSClosure: JSObject, JSClosureProtocol {
     }
 
     override public var jsValue: JSValue {
-        .function(JSFunction(id: self.id))
+        .object(self)
     }
 
     #if compiler(>=5.5) && (!hasFeature(Embedded) || os(WASI))

Sources/JavaScriptKit/FundamentalObjects/JSFunction.swift

@@ -105,7 +105,7 @@ public class JSFunction: JSObject {
     }
 
     override public var jsValue: JSValue {
-        .function(self)
+        .object(self)
     }
 }
 

Sources/JavaScriptKit/JSValue.swift

@@ -65,6 +65,7 @@ public enum JSValue: Equatable {
     public var function: JSFunction? {
         switch self {
         case .function(let function): return function
+        case .object(let object as JSFunction): return object
         default: return nil
         }
     }