fix(rsplat): resize images client-side before 3D generation, pass through fal.ai errors

Mobile photos (12MP+) were causing generation failures due to large base64 payloads.
Now resizes to max 1024px before sending. Server now returns actual fal.ai error
messages instead of generic "3D generation failed".

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

modules/rsplat/components/folk-splat-viewer.ts

@@ -521,15 +521,13 @@ export class FolkSplatViewer extends HTMLElement {
       submitBtn.disabled = true;
       actions.style.display = "none";
       progress.style.display = "block";
-      status.textContent = "";
+      status.textContent = "Preparing image...";
 
       try {
-        const reader = new FileReader();
-        const dataUrl = await new Promise<string>((resolve) => {
-          reader.onload = () => resolve(reader.result as string);
-          reader.readAsDataURL(selectedFile!);
-        });
+        // Resize image to max 1024px to reduce payload and improve API success
+        const dataUrl = await this.resizeImage(selectedFile!, 1024);
 
+        status.textContent = "Generating 3D model...";
         const res = await fetch("/api/3d-gen", {
           method: "POST",
           headers: { "Content-Type": "application/json" },
@@ -572,6 +570,30 @@ export class FolkSplatViewer extends HTMLElement {
     });
   }
 
+  // ── Image helpers ──
+
+  private resizeImage(file: File, maxSize: number): Promise<string> {
+    return new Promise((resolve, reject) => {
+      const img = new Image();
+      img.onload = () => {
+        let { width, height } = img;
+        if (width > maxSize || height > maxSize) {
+          const scale = maxSize / Math.max(width, height);
+          width = Math.round(width * scale);
+          height = Math.round(height * scale);
+        }
+        const canvas = document.createElement("canvas");
+        canvas.width = width;
+        canvas.height = height;
+        const ctx = canvas.getContext("2d")!;
+        ctx.drawImage(img, 0, 0, width, height);
+        resolve(canvas.toDataURL("image/jpeg", 0.9));
+      };
+      img.onerror = () => reject(new Error("Failed to load image"));
+      img.src = URL.createObjectURL(file);
+    });
+  }
+
   // ── Viewer ──
 
   private renderViewer() {

server/index.ts

@@ -998,9 +998,18 @@ app.post("/api/3d-gen", async (c) => {
 		});
 
 		if (!res.ok) {
-			const err = await res.text();
-			console.error("[3d-gen] fal.ai error:", err);
-			return c.json({ error: "3D generation failed" }, 502);
+			const errText = await res.text();
+			console.error("[3d-gen] fal.ai error:", res.status, errText);
+			let detail = "3D generation failed";
+			try {
+				const parsed = JSON.parse(errText);
+				if (parsed.detail) {
+					detail = typeof parsed.detail === "string" ? parsed.detail
+						: Array.isArray(parsed.detail) ? parsed.detail[0]?.msg || detail
+						: detail;
+				}
+			} catch {}
+			return c.json({ error: detail }, 502);
 		}
 
 		const data = await res.json();