feat: scope filterable fields to agent type and update active filters on selection change

lib/features/agents/presentation/providers/search_agents_provider.dart

@@ -78,7 +78,7 @@ class SearchAgentsNotifier extends StateNotifier<SearchAgentsState> {
     try {
       final results = await Future.wait([
         _repository.getAgentTypes(),
-        _repository.getFilterableFields(),
+        _repository.getFilterableFields(agentTypeId: state.selectedAgentTypeId),
       ]);
       if (!mounted) return;
       state = state.copyWith(
@@ -92,6 +92,28 @@ class SearchAgentsNotifier extends StateNotifier<SearchAgentsState> {
     }
   }
 
+  /// Re-fetch filterable fields scoped to the currently selected agent type.
+  /// Called whenever the user switches agent types so irrelevant filters disappear.
+  Future<void> _refreshFilterFields(String? agentTypeId) async {
+    try {
+      final fields =
+          await _repository.getFilterableFields(agentTypeId: agentTypeId);
+      if (!mounted) return;
+      // Drop any active filter slugs that no longer exist in the new list.
+      final validSlugs = fields.map((f) => f.slug).toSet();
+      final culled = <String, List<String>>{};
+      state.activeFilters.forEach((k, v) {
+        if (validSlugs.contains(k)) culled[k] = v;
+      });
+      state = state.copyWith(
+        filterFields: fields,
+        activeFilters: culled,
+      );
+    } catch (_) {
+      // Keep existing fields if the refresh fails; user can retry.
+    }
+  }
+
   Future<void> _fetchAgents({required int page, bool append = false}) async {
     try {
       final response = await _repository.searchAgents(
@@ -135,6 +157,7 @@ class SearchAgentsNotifier extends StateNotifier<SearchAgentsState> {
       isLoading: true,
       currentPage: 1,
     );
+    _refreshFilterFields(agentTypeId);
     _fetchAgents(page: 1);
   }