fix: ensure useFillHeight recalculates when element appears (v-if)

src/composables/useFillHeight.js

@@ -1,4 +1,4 @@
-import { onMounted, onUnmounted, ref, nextTick } from 'vue'
+import { onMounted, onUnmounted, ref, nextTick, watch } from 'vue'
 import { UI_CONFIG } from '../config/ui'
 
 export function useFillHeight(elementRef, extraMargin = 0) {
@@ -29,6 +29,13 @@ export function useFillHeight(elementRef, extraMargin = 0) {
     
     // Also update after a short delay to ensure layout is settled (e.g. sidebar transitions)
     setTimeout(updateHeight, 300)
+
+    // Watch for element appearing (v-if) or changing
+    watch(elementRef, () => {
+      nextTick(updateHeight)
+      // Additional update for layout stability
+      setTimeout(updateHeight, 100)
+    })
   })
 
   onUnmounted(() => {