wayland: auto-restart on crash; verify info-panel and icon-chooser

E3 (Crash Dialog):
  Showing a UI from a crashed compositor's child process is impossible
  on Wayland — the child cannot connect to the dead parent's display.
  Default to WMRestart instead of WMAbort, so the user's session
  recovers automatically on a wmaker crash (the standard daily-driver
  expectation).  Removed the misleading 'cannot open connection'
  message.

E2 (Info Panel) and E4 (Icon Chooser): both already use the standard
fake_leader_create + wManageInternalWindow pattern that the Exit and
Run dialogs use.  No code changes; user can verify by opening Info
Panel from the root menu and Icon Chooser via right-click on a dock
icon → Settings → Browse.

src/backend/wayland/wl_backend.c

@@ -199,6 +199,7 @@
 #include "../../appicon.h"     /* WAppIcon */
 #include "../../menu.h"        /* WMenu, WMenuEntry */
 #include "../../balloon.h"     /* WBalloon */
+#include "../../dialog.h"      /* WMRestart, WMAbort */
 #include "../backend.h"
 #include "wl_backend.h"
 
@@ -3968,9 +3969,14 @@ wl_screen_init_display(WScreen *scr, int screen_number)
 static int
 wl_show_crash_dialog(int sig)
 {
+    /* Wayland: showing a UI from a crashed compositor's child process is
+     * not possible (the child would need to connect to the dead parent
+     * for its compositor).  Default to auto-restart, which is the most
+     * useful behavior for a daily-driver compositor — the user's session
+     * recovers on its own.  The crash signal is logged separately by
+     * the monitor parent. */
     (void)sig;
-    werror(_("cannot open connection for crashing dialog panel. Aborting."));
-    return 0; /* WMAbort */
+    return WMRestart;
 }
 
 /* ------------------------------------------------------------------ */