ui : keep reasoning submenu visible regardless of model state

tools/ui/src/lib/components/app/chat/ChatForm/ChatFormActions/ChatFormActionAdd/ChatFormActionAddSheet.svelte

@@ -92,7 +92,7 @@
 								<ChevronRight class="{ICON_CLASS_DEFAULT} shrink-0" />
 							{/if}
 
-							{#if reasoning.thinkingEnabled}
+							{#if reasoning.isReasoningActive}
 								<Lightbulb class="{ICON_CLASS_DEFAULT} shrink-0 text-amber-400" />
 							{:else if reasoning.isOff}
 								<LightbulbOff class="{ICON_CLASS_DEFAULT} shrink-0 text-muted-foreground" />

tools/ui/src/lib/hooks/use-reasoning-menu.svelte.ts

@@ -92,6 +92,9 @@ export function useReasoningMenu(): UseReasoningMenuReturn {
 		get thinkingEnabled() {
 			return thinkingEnabled;
 		},
+		get isReasoningActive() {
+			return isReasoningActive;
+		},
 		tokenLabel(level: ReasoningEffortLevel): string | null {
 			if (level.value === ReasoningEffort.DEFAULT) return 'Model default';