fix: load tasks via TasksApi in Knowledge view, remove tab counts

Tasks are not part of the knowledge API (backend rejects type=task).
When the Tasks tab is selected, fetch from /api/tasks and convert to
KnowledgeItem. Also removes per-type counts from tab labels to prevent
tabs from awkwardly resizing when counts load.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/screens/knowledge/knowledge_screen.dart

@@ -74,15 +74,7 @@ class _KnowledgeScreenState extends ConsumerState<KnowledgeScreen>
     });
   }
 
-  String _tabLabel(int index, Map<String, int> counts) {
-    final tab = _kTabs[index];
-    if (tab.type == null) {
-      final total = counts.values.fold(0, (a, b) => a + b);
-      return total > 0 ? 'All ($total)' : 'All';
-    }
-    final count = counts[tab.type];
-    return count != null && count > 0 ? '${tab.label} ($count)' : tab.label;
-  }
+  String _tabLabel(int index) => _kTabs[index].label;
 
   @override
   Widget build(BuildContext context) {
@@ -119,7 +111,7 @@ class _KnowledgeScreenState extends ConsumerState<KnowledgeScreen>
           tabAlignment: TabAlignment.start,
           tabs: List.generate(
             _kTabs.length,
-            (i) => Tab(text: _tabLabel(i, state.counts)),
+            (i) => Tab(text: _tabLabel(i)),
           ),
         ),
       ),