fix(dashboard): sticky filter row no longer overlays sidebar — layout, not z-index

ListControls was sticky with z-10 + bg-cf-surface/95 + backdrop-blur,
which created a stacking context and let the row paint across the
sidebar column when scrolled.

Layout fix:
- ListControls drops z-10 + backdrop-blur + /95 translucency. Solid
  bg-cf-surface now opaquely occludes scrolled rows underneath
  without needing z-index to win against siblings.
- main gets `isolate` (Tailwind alias for isolation: isolate). Any
  z-index used inside the main column is trapped to that stacking
  context. Even if a child component reaches for z-N, it can't
  punch through to the Sidebar paint root anymore.

161/161 vitest + typecheck clean.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: fahchen

dashboard/ui/src/components/ListControls.tsx

@@ -36,7 +36,7 @@ export default function ListControls({
 
   return (
     <div
-      className="sticky top-0 z-10 flex flex-wrap items-center gap-3 rounded-xl border border-cf-border bg-cf-surface/95 px-4 py-3 backdrop-blur"
+      className="sticky top-0 flex flex-wrap items-center gap-3 rounded-xl border border-cf-border bg-cf-surface px-4 py-3"
       data-testid="list-controls"
     >
       <div className="min-w-[14rem] flex-1">

dashboard/ui/src/routes/RootLayout.tsx

@@ -120,7 +120,7 @@ export default function RootLayout() {
               <SidebarFooterContent />
             </Sidebar.Footer>
           </Sidebar>
-          <main className="relative flex-1 overflow-auto px-10 py-8">
+          <main className="relative isolate flex-1 overflow-auto px-10 py-8">
             <MobileSidebarTrigger />
             <Outlet />
           </main>