Keep the lock off the stacked editor while a dashboard is arranged

The phone path draws through DashboardView in both modes, so a locked
dashboard came out with dead controls while it was being arranged — the
canvas path hands editing to its own grid and never mounts the lock.
DashboardView takes `editing` and skips LockedProvider for it; reading a
locked dashboard stacked still locks. Guarded in mobile.spec.ts.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K1moruzue2kTJd3uVisgNk

frontend/src/components/Dashboard/DashboardEditor.tsx

@@ -461,6 +461,7 @@ export function DashboardEditor({
         <DashboardView
           dashboard={draft}
           stacked
+          editing={edit}
           renderWidget={edit ? pickable : undefined}
         />
       </div>

frontend/src/components/Dashboard/DashboardView.tsx

@@ -306,6 +306,7 @@ export function DashboardView({
   renderWidget,
   stacked,
   rail,
+  editing,
 }: {
   dashboard: Dashboard
   renderWidget?: (widget: WidgetDef) => React.ReactNode
@@ -313,6 +314,9 @@ export function DashboardView({
   stacked?: boolean
   /** Whether the panel carries a rail, which takes a column of the canvas. */
   rail?: boolean
+  /** Being arranged rather than used, so the lock is not mounted — the
+   *  stacked editor draws through here, where the canvas draws its own grid. */
+  editing?: boolean
 }) {
   const all = widgetsOf(dashboard)
   if (all.length === 0) {
@@ -337,20 +341,26 @@ export function DashboardView({
     : all
   const columns = columnsOf(dashboard)
 
+  const grid = (
+    <PaletteProvider dashboard={dashboard}>
+      <WidgetGrid
+        dashboard={dashboard}
+        widgets={widgets}
+        columns={columns}
+        stacked={stacked}
+        rail={rail}
+        renderWidget={renderWidget}
+      />
+    </PaletteProvider>
+  )
+
   return (
     <LookProvider dashboard={dashboard}>
-      <LockedProvider dashboard={dashboard}>
-        <PaletteProvider dashboard={dashboard}>
-          <WidgetGrid
-            dashboard={dashboard}
-            widgets={widgets}
-            columns={columns}
-            stacked={stacked}
-            rail={rail}
-            renderWidget={renderWidget}
-          />
-        </PaletteProvider>
-      </LockedProvider>
+      {editing ? (
+        grid
+      ) : (
+        <LockedProvider dashboard={dashboard}>{grid}</LockedProvider>
+      )}
     </LookProvider>
   )
 }