feat: replace manual byte-buffer parsing with native C list creation in Directory.list()

The C directoryListCallback now directly builds a Wren list using wrenSetSlotNewList and wrenInsertInList, eliminating the temporary byte buffer that required manual splitting in Wren. The Wren side is simplified to a single return of the scheduler result. Additionally, the wrenCall and wrenCaptureValue functions are hardened: wrenCall discards extra temporary slots and calls with arity 0, wrenCaptureValue properly roots/unroots object values during handle creation, and the debug stack trace printer skips stub functions with NULL module pointers. A new test case verifies that wrenCall correctly ignores extra temporary slots on the stack.

test/api/call.c

@@ -73,6 +73,15 @@ void callRunTests(WrenVM* vm)
   wrenSetSlotBytes(vm, 2, "b\0y\0t\0e", 7);
   wrenCall(vm, two);
   
+  // Call ignores with extra temporary slots on stack.
+  wrenEnsureSlots(vm, 10);
+  wrenSetSlotValue(vm, 0, callClass);
+  for (int i = 1; i < 10; i++)
+  {
+    wrenSetSlotDouble(vm, i, i * 0.1);
+  }
+  wrenCall(vm, one);
+  
   wrenReleaseValue(vm, callClass);
   wrenReleaseValue(vm, noParams);
   wrenReleaseValue(vm, zero);

test/api/call.wren

@@ -33,3 +33,4 @@ class Call {
 // expect: two string another
 // expect: two null [a, b]
 // expect: two str [98, 0, 121, 0, 116, 0, 101]
+// expect: one 0.1