fix(search): rebuild the results pager only when the dictionary set changes

Background metadata loading rewrote the dictionaries flow several times
after startup, and every emission recreated the Pager: the results list
visibly collapsed and refilled. Distinct on the index paths that paging
actually uses, and seed the state synchronously instead of an empty list.

app/src/main/java/com/example/research/feature/search/SearchViewModel.kt

@@ -70,10 +70,12 @@ class SearchViewModel(
     private val activeDictionaries: StateFlow<List<com.example.research.core.domain.model.Dictionary>> =
         repository.dictionaries.map { dictList ->
             dictList.filter { it.isActive }
+        }.distinctUntilChanged { previous, current ->
+            previous.map { it.indexPath } == current.map { it.indexPath }
         }.stateIn(
             scope = viewModelScope,
             started = SharingStarted.WhileSubscribed(5000),
-            initialValue = emptyList()
+            initialValue = repository.dictionaries.value.filter { it.isActive }
         )
 
     init {