fix(catalog): keep Nitro editor stable during background polling

src/app/admin/import/furni/nitro-editor-dialog.tsx

@@ -16,7 +16,7 @@ import {
 	Save,
 	Sparkles,
 } from "lucide-react";
-import { useCallback, useEffect, useState } from "react";
+import { useEffect, useEffectEvent, useState } from "react";
 import { toast } from "sonner";
 import { NitroQualityPanel } from "@/components/admin/studio/nitro-quality-panel";
 import { NitroScale32Generator } from "@/components/admin/studio/nitro-scale32-generator";
@@ -188,40 +188,43 @@ export function NitroEditorDialog({
 		);
 	};
 
-	const fetchMetadata = useCallback(async () => {
-		if (!classname) return;
+	const closeAfterLoadError = useEffectEvent(() => onOpenChange(false));
+	useEffect(() => {
+		if (!open || !classname) return;
+		const controller = new AbortController();
+		setActiveTab("visual");
 		setLoading(true);
 		setJsonError(null);
-		try {
-			const res = await adminFetch(
-				`/api/admin/import/furni/nitro-editor?classname=${encodeURIComponent(classname)}`,
-			);
-			if (!res.ok) {
-				const err = await res.json().catch(() => ({}));
-				toast.error(err.error || "Failed to load .nitro metadata");
-				onOpenChange(false);
-				return;
+		setAutoDetectResult(null);
+		void (async () => {
+			try {
+				const res = await adminFetch(
+					`/api/admin/import/furni/nitro-editor?classname=${encodeURIComponent(classname)}`,
+					{ signal: controller.signal },
+				);
+				const data = await res.json();
+				if (controller.signal.aborted) return;
+				if (!res.ok) {
+					toast.error(data.error || "Failed to load .nitro metadata");
+					closeAfterLoadError();
+					return;
+				}
+				setMetadata(data.metadata);
+				setOriginalMetadata(structuredClone(data.metadata));
+				setJsonText(JSON.stringify(data.metadata, null, 2));
+				setFlags(data.flags);
+				setOriginalFlags({ ...data.flags });
+			} catch {
+				if (!controller.signal.aborted) {
+					toast.error("Network error loading .nitro metadata");
+					closeAfterLoadError();
+				}
+			} finally {
+				if (!controller.signal.aborted) setLoading(false);
 			}
-			const data = await res.json();
-			setMetadata(data.metadata);
-			setOriginalMetadata(JSON.parse(JSON.stringify(data.metadata)));
-			setJsonText(JSON.stringify(data.metadata, null, 2));
-			setFlags(data.flags);
-			setOriginalFlags({ ...data.flags });
-		} catch {
-			toast.error("Network error loading .nitro metadata");
-			onOpenChange(false);
-		} finally {
-			setLoading(false);
-		}
-	}, [classname, onOpenChange]);
-
-	useEffect(() => {
-		if (open && classname) {
-			setActiveTab("visual");
-			fetchMetadata();
-		}
-	}, [open, classname, fetchMetadata]);
+		})();
+		return () => controller.abort();
+	}, [open, classname]);
 
 	const handleTabChange = (newTab: string) => {
 		if (activeTab === "json" && newTab !== "json") {