Initial commit: DSH mind-map canvas monorepo

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/web/src/image-cache.ts

@@ -0,0 +1,31 @@
+/** Shared image loader for canvas card thumbnails. */
+const cache = new Map<string, HTMLImageElement | "loading" | "error">();
+
+export function getCachedImage(
+  url: string,
+  onUpdate: () => void,
+): HTMLImageElement | null {
+  const hit = cache.get(url);
+  if (hit instanceof HTMLImageElement) return hit;
+  if (hit === "loading" || hit === "error") return null;
+
+  cache.set(url, "loading");
+  const img = new Image();
+  img.decoding = "async";
+  // Best-effort; some CDNs block canvas without CORS — we still draw when allowed.
+  img.crossOrigin = "anonymous";
+  img.onload = () => {
+    cache.set(url, img);
+    onUpdate();
+  };
+  img.onerror = () => {
+    cache.set(url, "error");
+    onUpdate();
+  };
+  img.src = url;
+  return null;
+}
+
+export function imageLoadFailed(url: string): boolean {
+  return cache.get(url) === "error";
+}