fix(window): the title a program passes to gl_open / gvk_open reaches the window

The runtime opens a game's window before main, titled with the program's name, and
gl_open attached to it without passing its title on (render3d's gvk_open called win_open,
which returns early on Windows and opened a second window on macOS). win_set_title in
cocoa.ll / win32.ll (setTitle: / SetWindowTextW, UTF-8 -> UTF-16; a no-op without a window,
stubbed headless) retitles it from gl_open, and win_open on an open window retitles it on
both platforms.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

runtime/native/gl_win_nowin.ll

@@ -52,3 +52,8 @@ define ptr @win_native_instance() {
 entry:
   ret ptr null
 }
+
+define void @win_set_title(ptr %title) {
+entry:
+  ret void
+}