editor: outline lists no longer position:fixed (unstack the rail)

.cms-outline was in the shared fixed-panel selector, so every outline
level (tree, nested, slots) broke out of the rail flow and painted as
an opaque floating box stacked over the palette/nodes sections below -
nothing under it was clickable or draggable. The outline only ever
renders inside the rail, so it is now plain in-flow; standalone panels
(bar, dock, dialogs, dev, assistant, toast) keep their fixed rule.

🤖 Generated with Codebuff
Co-Authored-By: Codebuff <noreply@codebuff.com>

src/ui/styles.css

@@ -14,7 +14,7 @@ button:disabled { opacity: .35; cursor: default; }
 .cms-frame--editing { border: 2px dashed #5ee0a0; background: none; }
 .cms-frame__tag { position: absolute; top: -18px; left: -1px; padding: 1px 6px; font-size: 11px; background: #6aa7ff; color: #07080b; border-radius: 3px 3px 0 0; }
 
-.cms-bar, .cms-dock, .cms-dialog, .cms-outline, .cms-dev, .cms-assistant, .cms-toast {
+.cms-bar, .cms-dock, .cms-dialog, .cms-dev, .cms-assistant, .cms-toast {
   pointer-events: auto; position: fixed; z-index: 2147483001;
   background: #14161d; border: 1px solid #2a2d3a; border-radius: 10px; box-shadow: 0 8px 30px rgba(0,0,0,.45);
 }