fix: Qt6 Wayland crash — root cause identified, kded6 fix deployed

ROOT CAUSE: Qt6's auto-generated Wayland wrappers pass NULL proxies
to wl_*_add_listener() during initialization. The generated code stores
wlRegistryBind() return value in m_wl_* member without null check,
then init_listener() calls wl_*_add_listener(m_wl_*, ...) which
page-faults at null+8 (write to proxy->object.implementation).

FIX (kded6): wrapper script renames libqwayland.so to .disabled
before launching kded6.real. QT_QPA_PLATFORM=offscreen alone is not
sufficient — Qt6 still loads wayland plugin despite env var.

FIX (libwayland): null guards in redox.patch for wl_proxy_add_listener,
wl_proxy_get_version, wl_proxy_get_display. Blocked from compilation
by pre-existing relibc conflicts (open_memstream, signalfd_siginfo).

FIX (Qt6 wrappers): regex-based null guard insertion proven in concept.
Blocked by TOML recipe format not supporting backslash escape sequences.
Implementation plan: inject null guards via a separate build step script
rather than inline in recipe.toml.

local/recipes/wayland/libwayland/source/src/wayland-client.c

@@ -649,6 +649,12 @@ WL_EXPORT int
 wl_proxy_add_listener(struct wl_proxy *proxy,
 		      void (**implementation)(void), void *data)
 {
+	if (!proxy) {
+		fprintf(stderr, "FATAL: wl_proxy_add_listener(NULL) caller=%p -- returning error
+",
+		        __builtin_return_address(0));
+		return -1;
+	}
 	if (proxy->flags & WL_PROXY_FLAG_WRAPPER)
 		wl_abort("Proxy %p is a wrapper\n", proxy);
 
@@ -2442,6 +2448,7 @@ wl_proxy_get_user_data(struct wl_proxy *proxy)
 WL_EXPORT uint32_t
 wl_proxy_get_version(struct wl_proxy *proxy)
 {
+	if (!proxy) return 0;
 	return proxy->version;
 }
 
@@ -2560,6 +2567,7 @@ wl_proxy_get_interface(struct wl_proxy *proxy)
 WL_EXPORT struct wl_display *
 wl_proxy_get_display(struct wl_proxy *proxy)
 {
+	if (!proxy) return NULL;
 	return proxy->display;
 }