fix(ui): stabilize mobile keyboard viewport handling (#1026)

* fix(ui): stabilize mobile keyboard viewport handling

* fix(ui): tighten mobile keyboard viewport handling

* Avoid redundant keyboard open store writes

---------

Co-authored-by: vhqtvn <8930337+vhqtvn@users.noreply.github.com>
Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/stores/useUIStore.ts

@@ -482,6 +482,7 @@ interface UIStore {
   pendingFileNavigation: PendingFileNavigation | null;
   pendingFileFocusPath: string | null;
   isMobile: boolean;
+  isKeyboardOpen: boolean;
   isQuickOpenOpen: boolean;
   isCommandPaletteOpen: boolean;
   isHelpDialogOpen: boolean;
@@ -636,6 +637,7 @@ interface UIStore {
   setPadding: (size: number) => void;
   setCornerRadius: (radius: number) => void;
   setInputBarOffset: (offset: number) => void;
+  setKeyboardOpen: (open: boolean) => void;
   applyTypography: () => void;
   applyPadding: () => void;
   updateProportionalSidebarWidths: () => void;
@@ -722,6 +724,7 @@ export const useUIStore = create<UIStore>()(
         pendingFileNavigation: null,
         pendingFileFocusPath: null,
         isMobile: false,
+        isKeyboardOpen: false,
         isQuickOpenOpen: false,
         isCommandPaletteOpen: false,
         isHelpDialogOpen: false,
@@ -1467,6 +1470,10 @@ export const useUIStore = create<UIStore>()(
           set({ inputBarOffset: offset });
         },
 
+        setKeyboardOpen: (open) => {
+          set((state) => state.isKeyboardOpen === open ? state : { isKeyboardOpen: open });
+        },
+
         toggleFavoriteModel: (providerID, modelID) => {
           set((state) => {
             const exists = state.favoriteModels.some(