Split apart the frontend Editor type into SubscriptionsRouter and EditorHandle (#3923)

* Remove the unused Editor.raw/wasmMemory/wasmImport

* Split out Editor.subscriptions

* Replace editor.handle.* with editor.* (1 of 2)

* Replace editor.handle.* with editor.* (2 of 2)

* Replace Editor typedef with EditorHandle import

* Pluralize subscription-router and rename subscriptionsRef->subscriptionsRouter and editorRef->editorHandle

* Remove editor.ts

* Update the readme

* Fix demo art loading bug

frontend/src/utility-functions/network.ts

@@ -1,3 +1,5 @@
+import type { EditorHandle } from "@graphite/../wasm/pkg/graphite_wasm";
+
 export type RequestResult = { body: string; status: number };
 
 // Special implementation using the legacy XMLHttpRequest API that provides callbacks to get:
@@ -31,3 +33,23 @@ export function requestWithUploadDownloadProgress(
 
 	return [promise, xhrValue];
 }
+
+// If the URL hash fragment contains a demo artwork path (e.g. #demo/isometric-light), fetch and open it
+export async function loadDemoArtwork(editor: EditorHandle) {
+	const demoArtwork = window.location.hash.trim().match(/#demo\/(.*)/)?.[1];
+	if (!demoArtwork) return;
+
+	try {
+		const url = new URL(`/demo-artwork/${demoArtwork}.${editor.fileExtension()}`, document.location.href);
+		const response = await fetch(url);
+		if (!response.ok) throw new Error();
+
+		const filename = url.pathname.split("/").pop() || `Untitled.${editor.fileExtension()}`;
+		const content = await response.bytes();
+		editor.openFile(filename, content);
+
+		history.replaceState("", "", `${window.location.pathname}${window.location.search}`);
+	} catch {
+		// Do nothing
+	}
+}