fix: hide system prompt optimization in VS Code

Removes the system prompt optimization section from the Behavior page in VS Code runtime.
Updates settings search so the hidden option is not shown as available in VS Code.

packages/ui/src/lib/settings/search.ts

@@ -562,6 +562,7 @@ const SETTINGS_SEARCH_ITEMS: readonly SettingsSearchItem[] = [
     titleKey: 'settings.behavior.page.section.systemPromptOptimization',
     descriptionKey: 'settings.behavior.page.systemPromptOptimization.info',
     keywords: ['system prompt', 'tokens', 'context', 'optimize', 'minimal'],
+    isAvailable: (ctx) => !ctx.isVSCode,
   },
   {
     id: 'behavior.system-prompt',