wayland: fix dock ghost shadow z-order (render below icon)

The dock_shadow was rendering above the dragged icon because:
1. It was in WL_LAYER_OVERLAY/DOCK, above the dock icons in WL_LAYER_FLOATING
2. wl_stacking_restack could not order nodes across different parent trees
3. wl_window_map auto-raised on map, undoing any prior restack

Fixes:
- Place dock_shadow in WL_LAYER_FLOATING (where WMDockLevel=5 maps)
- Rewrite wl_stacking_restack to reparent nodes into the same tree
  and use wlr_scene_node_place_below for guaranteed ordering
- Remove auto-raise from wl_window_map (explicit wRaiseFrame handles it)

src/backend/wayland/wl_screen.c

@@ -503,8 +503,8 @@ wl_screen_create_internals(WScreen *scr)
             dsfb->id = wl_state.next_synthetic_id++;
             dsfb->width = sz;
             dsfb->height = sz;
-            struct wlr_scene_tree *ds_parent = wl_state.level_trees[WL_LAYER_NORMAL]
-                ? wl_state.level_trees[WL_LAYER_NORMAL] : &wl_state.scene->tree;
+            struct wlr_scene_tree *ds_parent = wl_state.level_trees[WL_LAYER_FLOATING]
+                ? wl_state.level_trees[WL_LAYER_FLOATING] : &wl_state.scene->tree;
             dsfb->tree = wlr_scene_tree_create(ds_parent);
             if (dsfb->tree) {
                 dsfb->scene_buf = wlr_scene_buffer_create(dsfb->tree, &dsfb->base);

src/backend/wayland/wl_stacking.c

@@ -124,30 +124,36 @@ wl_stacking_restack(WNativeWindow *windows, int count)
      * Process bottom-to-top: last raise_to_top call wins, so the
      * window at index 0 ends up on top within its level bucket.
      *
-     * Each window is represented by its toplevel frame_buf ID.  We
-     * raise fb->tree — the grouping tree that owns both the frame
-     * pixel buffer and the reparented client surface — so the entire
-     * window moves as one atomic unit.  Child frame_bufs (titlebar,
-     * resizebar) are already children of fb->tree and move with it. */
+     * When windows span different parent trees (level buckets),
+     * raise_to_top only orders within a parent.  Use place_below
+     * for cross-parent ordering of adjacent entries. */
     int i;
-    for (i = count - 1; i >= 0; i--) {
+    /* Collect nodes */
+    struct wlr_scene_node *nodes[64];
+    int n = 0;
+    for (i = 0; i < count && n < 64; i++) {
         WNativeWindow win = windows[i];
         struct wl_frame_buf *fb = frame_buf_find(win);
+        struct wlr_scene_node *node = NULL;
         if (fb) {
-            /* Raise the grouping tree: moves frame + client together. */
-            if (fb->tree)
-                wlr_scene_node_raise_to_top(&fb->tree->node);
-            else if (fb->scene_buf)
-                wlr_scene_node_raise_to_top(&fb->scene_buf->node);
-            continue;
+            node = fb->tree ? &fb->tree->node : (fb->scene_buf ? &fb->scene_buf->node : NULL);
+        } else {
+            struct wl_toplevel_view *v = wl_find_view_by_id(win);
+            if (v && v->scene_node)
+                node = &v->scene_node->node;
         }
-        /* Fallback: unframed toplevel view (no frame_buf). */
-        struct wl_toplevel_view *v = wl_find_view_by_id(win);
-        if (v) {
-            wl_list_remove(&v->link);
-            wl_list_insert(&wl_state.toplevel_list, &v->link);
-            if (v->scene_node)
-                wlr_scene_node_raise_to_top(&v->scene_node->node);
+        if (node) nodes[n++] = node;
+    }
+    /* Place in order: nodes[0] on top, nodes[n-1] on bottom.
+     * Raise top node, then place each subsequent one below its predecessor. */
+    for (i = 0; i < n; i++) {
+        if (i == 0) {
+            wlr_scene_node_raise_to_top(nodes[i]);
+        } else {
+            /* Reparent to same parent if needed for place_below to work */
+            if (nodes[i]->parent != nodes[i-1]->parent)
+                wlr_scene_node_reparent(nodes[i], (struct wlr_scene_tree *)nodes[i-1]->parent);
+            wlr_scene_node_place_below(nodes[i], nodes[i-1]);
         }
     }
 }

src/backend/wayland/wl_window.c

@@ -94,12 +94,9 @@ wl_window_map(WNativeWindow win)
                 return;  /* parent not visible yet */
         }
         wlr_scene_node_set_enabled(&fb->scene_buf->node, true);
-        /* Raise the tree (raises entire window assembly together) */
         if (fb->tree) {
             wlr_scene_node_set_enabled(&fb->tree->node, true);
-            wlr_scene_node_raise_to_top(&fb->tree->node);
-        } else if (!fb->parent_id)
-            wlr_scene_node_raise_to_top(&fb->scene_buf->node);
+        }
         /* Also enable children (and grandchildren) */
         struct wl_frame_buf *child;
         wl_list_for_each(child, &wl_state.frame_list, link) {