Refresh the homepage and improve export and draft guidance

shared/protocol.ts

@@ -56,6 +56,23 @@ export const datasetSchema = z
       .max(4096),
   })
   .superRefine((d, ctx) => {
+    const paths = new Set(d.assets.map((asset) => asset.path));
+    const requiredPaths =
+      d.source === "plugin"
+        ? ["terrain.json.gz"]
+        : [
+            "map.png",
+            ...d.viewpoints.flatMap((point) =>
+              faces.map((face) => `${point.id}/${face}.png`),
+            ),
+          ];
+    for (const path of requiredPaths) {
+      if (!paths.has(path))
+        ctx.addIssue({
+          code: "custom",
+          message: `Missing required export asset: ${path}`,
+        });
+    }
     if (new Set(d.viewpoints.map((p) => p.id)).size !== d.viewpoints.length)
       ctx.addIssue({ code: "custom", message: "Viewpoint IDs must be unique" });
     if (new Set(d.assets.map((a) => a.path)).size !== d.assets.length)