style(desktop): drop the titlebar and statusbar edge rules

The window chrome bracketed the workspace with a 1px rule top and bottom.
Both bars already paint the sidebar surface, so the rules divided one
continuous color rather than separating two.

apps/desktop/src/app/contrib/controller.tsx

@@ -665,7 +665,7 @@ export function ContribController() {
                   tree-published --workspace-left/right vars (pure CSS, no rect
                   threading), clamped to clear the REAL TitlebarControls
                   clusters (fixed, z-70); center is truly window-centered. */}
-          <div className="relative flex h-[34px] shrink-0 items-center border-b border-(--ui-stroke-tertiary) bg-(--ui-sidebar-surface-background) text-xs">
+          <div className="relative flex h-[34px] shrink-0 items-center bg-(--ui-sidebar-surface-background) text-xs">
             {/* Drag strips, AppShell-style: cut to AVOID the fixed control
                 clusters instead of overlapping them — Electron's no-drag
                 carve-out of fixed/transformed elements is unreliable, so a

apps/desktop/src/app/shell/statusbar-controls.tsx

@@ -92,7 +92,7 @@ export function StatusbarControls({ className, leftItems = [], items = [], ...pr
       <ContextMenuTrigger asChild>
         <footer
           className={cn(
-            'flex h-5 shrink-0 items-stretch justify-between gap-2 border-t border-(--ui-stroke-tertiary) bg-(--ui-sidebar-surface-background) px-1 py-0 text-(--ui-text-tertiary) [-webkit-app-region:no-drag]',
+            'flex h-5 shrink-0 items-stretch justify-between gap-2 bg-(--ui-sidebar-surface-background) px-1 py-0 text-(--ui-text-tertiary) [-webkit-app-region:no-drag]',
             className
           )}
           data-slot="statusbar"