refactor: tighten nitro editor JSON typing with generic path helpers

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

@@ -47,8 +47,7 @@ interface NitroVisualization {
 }
 
 // The .nitro metadata is untyped JSON from disk; typed only for the fields the
-// editor reads/writes, with an index signature so the generic path helpers can
-// traverse arbitrary nested keys.
+// editor reads/writes. Unknown keys are traversed via the path helpers below.
 interface NitroMetadata {
 	visualizationType?: string;
 	logicType?: string;
@@ -59,19 +58,18 @@ interface NitroMetadata {
 		};
 	};
 	visualizations?: NitroVisualization[];
-	[key: string]: unknown;
 }
 
 type JsonObject = Record<string, unknown>;
 
-function updateNested<T extends JsonObject>(
+function updateNested<T extends object>(
 	obj: T,
 	path: string,
 	value: unknown,
 ): T {
 	const clone: T = JSON.parse(JSON.stringify(obj));
 	const keys = path.split(".");
-	let current: JsonObject = clone;
+	let current: JsonObject = clone as JsonObject;
 	for (let i = 0; i < keys.length - 1; i++) {
 		const next = current[keys[i]];
 		if (!next || typeof next !== "object" || Array.isArray(next)) {
@@ -83,14 +81,14 @@ function updateNested<T extends JsonObject>(
 	return clone;
 }
 
-function getNested(obj: unknown, path: string, fallback?: unknown): unknown {
+function getNested<T>(obj: unknown, path: string, fallback: T): T {
 	const keys = path.split(".");
 	let current: unknown = obj;
 	for (const key of keys) {
 		if (current == null || typeof current !== "object") return fallback;
 		current = (current as JsonObject)[key];
 	}
-	return current ?? fallback;
+	return current === undefined ? fallback : (current as T);
 }
 
 const ALL_DIRECTIONS = [0, 1, 2, 3, 4, 5, 6, 7];
@@ -255,14 +253,12 @@ export function NitroEditorDialog({
 
 	// ── Visual tab helpers ──
 
-	const dims = (
-		metadata
-			? getNested(metadata, "logic.model.dimensions", { x: 1, y: 1, z: 0 })
-			: { x: 1, y: 1, z: 0 }
-	) as { x: number; y: number; z: number };
-	const directions = (
-		metadata ? getNested(metadata, "logic.model.directions", [0]) : [0]
-	) as number[];
+	const dims = metadata
+		? getNested(metadata, "logic.model.dimensions", { x: 1, y: 1, z: 0 })
+		: { x: 1, y: 1, z: 0 };
+	const directions = metadata
+		? getNested(metadata, "logic.model.directions", [0])
+		: [0];
 
 	const setDim = (axis: "x" | "y" | "z", value: string) => {
 		const num =
@@ -271,11 +267,7 @@ export function NitroEditorDialog({
 	};
 
 	const toggleDirection = (dir: number) => {
-		const current = getNested(
-			metadata,
-			"logic.model.directions",
-			[0],
-		) as number[];
+		const current = getNested(metadata, "logic.model.directions", [0]);
 		const next = current.includes(dir)
 			? current.filter((d: number) => d !== dir)
 			: [...current, dir].sort((a: number, b: number) => a - b);