Refine: Make persistent navbar viewport-aware

This commit enhances the behavior of the persistent desktop navbar.
Previously, if `desktopNavbarPersistent` was true, the main content
would always shift to accommodate the sidebar on medium screens and up.

Now, the content shifting is also conditional on available viewport width:

- The main content wrapper in `App.vue` now tracks `window.innerWidth`.
- A `SHIFT_THRESHOLD` is defined (currently 880px), calculated from
  NAVBAR_WIDTH (240px) + MIN_CONTENT_WIDTH (640px).
- If `ui.sidebarOpen` and `ui.desktopNavbarPersistent` are both true,
  the `md:pl-60` class (to shift content) is only applied if
  `viewportWidth.value >= SHIFT_THRESHOLD`.
- If the viewport width is below this threshold (but still potentially
  above the 'md' breakpoint), the persistent sidebar will overlay the
  content, similar to a non-persistent or mobile sidebar, preventing
  the main content area from becoming too cramped.

This provides a more refined and responsive user experience for you
if you enable the persistent navbar feature on varying screen sizes.

ui/src/App.vue

@@ -1,10 +1,32 @@
 <script setup>
-import { watchEffect, computed } from 'vue' // Added computed
+import { watchEffect, computed, ref, onMounted, onUnmounted } from 'vue' // ensure all are imported
 import TopBar from '@/components/ui/TopBar.vue'
 import NavBar from '@/components/ui/NavBar.vue'
 import { useUi } from '@/stores/useUi'
 
 const ui = useUi()
+const viewportWidth = ref(0) // New reactive variable
+
+const updateViewportWidth = () => { // New function
+  viewportWidth.value = window.innerWidth
+}
+
+onMounted(() => { // New lifecycle hook
+  updateViewportWidth()
+  window.addEventListener('resize', updateViewportWidth)
+})
+
+onUnmounted(() => { // New lifecycle hook
+  window.removeEventListener('resize', updateViewportWidth)
+})
+
+const NAVBAR_WIDTH = 240 // Defined constant
+const MIN_CONTENT_WIDTH = 640 // Defined constant
+const SHIFT_THRESHOLD = NAVBAR_WIDTH + MIN_CONTENT_WIDTH // Calculated threshold
+
+const shouldShiftContent = computed(() => { // New computed property
+  return ui.sidebarOpen &&          ui.desktopNavbarPersistent &&          viewportWidth.value >= SHIFT_THRESHOLD
+})
 
 watchEffect(() => {
   const root = document.documentElement
@@ -63,8 +85,8 @@ const transitionDurationStyle = computed(() => {
 
   <!-- wrapper: deja espacio para TopBar (pt-14 = 56px) y, en desktop, para NavBar (pl-60) -->
   <div :class="[
-    'pt-14 min-h-screen transition-[padding-left] duration-200',
-    (ui.sidebarOpen && ui.desktopNavbarPersistent) ? 'md:pl-60' : '',
+    'pt-14 min-h-screen transition-[padding-left] duration-200', // Keep existing transition
+    shouldShiftContent.value ? 'md:pl-60' : '', // Use the computed property
     // The global style.css will handle base background and text color via body styling
     // but we can keep specific overrides here if needed or theme classes.
     // ui.theme === 'dark' ? 'bg-gray-800 text-gray-100' : 'bg-gray-100 text-gray-900'