feat(vscode-ide-companion/completion): enhance completion menu performance and refresh logic

Implement item comparison to prevent unnecessary re-renders when completion items
haven't actually changed. Optimize refresh logic to only trigger when workspace
files content changes. Improve completion menu stability and responsiveness.

refactor(vscode-ide-companion/handlers): remove SettingsMessageHandler and consolidate functionality

Move setApprovalMode functionality from SettingsMessageHandler to SessionMessageHandler
to reduce code duplication and simplify message handling architecture. Remove unused
settings-related imports and clean up message router configuration.

chore(vscode-ide-companion/ui): minor UI improvements and code cleanup

Consolidate imports in SessionSelector component.
Remove debug console log statement from FileMessageHandler.
Move getTimeAgo utility function to sessionGrouping file and remove obsolete timeUtils file.
Clean up completion menu CSS classes.

packages/vscode-ide-companion/src/webview/hooks/useCompletionTrigger.ts

@@ -131,12 +131,55 @@ export function useCompletionTrigger(
     [getCompletionItems, LOADING_ITEM, TIMEOUT_ITEM],
   );
 
+  // Helper function to compare completion items arrays
+  const areItemsEqual = (
+    items1: CompletionItem[],
+    items2: CompletionItem[],
+  ): boolean => {
+    if (items1.length !== items2.length) {
+      return false;
+    }
+
+    // Compare each item by stable fields (ignore non-deterministic props like icons)
+    for (let i = 0; i < items1.length; i++) {
+      const a = items1[i];
+      const b = items2[i];
+      if (a.id !== b.id) {
+        return false;
+      }
+      if (a.label !== b.label) {
+        return false;
+      }
+      if ((a.description ?? '') !== (b.description ?? '')) {
+        return false;
+      }
+      if (a.type !== b.type) {
+        return false;
+      }
+      if ((a.value ?? '') !== (b.value ?? '')) {
+        return false;
+      }
+      if ((a.path ?? '') !== (b.path ?? '')) {
+        return false;
+      }
+    }
+
+    return true;
+  };
+
   const refreshCompletion = useCallback(async () => {
     if (!state.isOpen || !state.triggerChar) {
       return;
     }
     const items = await getCompletionItems(state.triggerChar, state.query);
-    setState((prev) => ({ ...prev, items }));
+
+    // Only update state if items have actually changed
+    setState((prev) => {
+      if (areItemsEqual(prev.items, items)) {
+        return prev;
+      }
+      return { ...prev, items };
+    });
   }, [state.isOpen, state.triggerChar, state.query, getCompletionItems]);
 
   useEffect(() => {