fix(app): polish workspace navigation surfaces

Use mobile action sheets and long-press file menus while preserving provider context across sheet portals. Keep sidebar and file-pane glyphs on shared visual rails, avoid scrollbar layout shifts, and hide keyboard affordances where shortcuts are unavailable.

packages/app/src/components/tool-call-sheet.tsx

@@ -114,6 +114,7 @@ export function ToolCallSheetProvider({ children }: ToolCallSheetProviderProps)
       {children}
       <IsolatedBottomSheetModal
         ref={bottomSheetRef}
+        contextBridge={null}
         snapPoints={snapPoints}
         index={0}
         enableDynamicSizing={false}