refactor: change wrenCompileSource to return ObjClosure instead of ObjFiber and inline import execution

The compileInModule function now returns a closure directly instead of wrapping it in a fiber, simplifying the compilation pipeline and removing unnecessary fiber overhead for module imports. The wrenImportModule function is moved into wren_vm.c and rewritten to execute the imported module's closure immediately rather than returning a fiber for deferred execution. This change also adds a test for yielding from an imported module to verify correct behavior with the new execution model.

src/optional/wren_opt_meta.c

@@ -14,18 +14,18 @@ void metaCompile(WrenVM* vm)
   bool printErrors = wrenGetSlotBool(vm, 3);
 
   // TODO: Allow passing in module?
-  ObjFiber* fiber = wrenCompileSource(vm, "main", source,
-                                      isExpression, printErrors);
-  
+  ObjClosure* closure = wrenCompileSource(vm, "main", source,
+                                          isExpression, printErrors);
+
   // Return the result. We can't use the public API for this since we have a
-  // bare ObjFiber*.
-  if (fiber == NULL)
+  // bare ObjClosure*.
+  if (closure == NULL)
   {
     vm->apiStack[0] = NULL_VAL;
   }
   else
   {
-    vm->apiStack[0] = OBJ_VAL(fiber);
+    vm->apiStack[0] = OBJ_VAL(closure);
   }
 }
 

src/optional/wren_opt_meta.wren

@@ -10,11 +10,11 @@ class Meta {
   static eval(source) {
     if (!(source is String)) Fiber.abort("Source code must be a string.")
 
-    var fiber = compile_(source, false, false)
+    var closure = compile_(source, false, false)
     // TODO: Include compile errors.
-    if (fiber == null) Fiber.abort("Could not compile source code.")
+    if (closure == null) Fiber.abort("Could not compile source code.")
 
-    fiber.call()
+    closure.call()
   }
 
   static compileExpression(source) {

src/optional/wren_opt_meta.wren.inc

@@ -12,11 +12,11 @@ static const char* metaModuleSource =
 "  static eval(source) {\n"
 "    if (!(source is String)) Fiber.abort(\"Source code must be a string.\")\n"
 "\n"
-"    var fiber = compile_(source, false, false)\n"
+"    var closure = compile_(source, false, false)\n"
 "    // TODO: Include compile errors.\n"
-"    if (fiber == null) Fiber.abort(\"Could not compile source code.\")\n"
+"    if (closure == null) Fiber.abort(\"Could not compile source code.\")\n"
 "\n"
-"    fiber.call()\n"
+"    closure.call()\n"
 "  }\n"
 "\n"
 "  static compileExpression(source) {\n"