fix(studio): accept numeric scene/content ids (template inputs now load)

THE bug behind 'nothing changed': parseScene required a STRING id, but the V2
relational scene assembly serializes numeric ids (scene 23, content 136) — so every
template scene was rejected → 0 scenes → studio fell back to its default 2-layer
title/subtitle. Coerce numeric ids to string. Verified: insta-promo project now
parses 1 scene / 6 layers (frl_c1t1-t4 text + frl_c1m1/m2 media).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lib/studio-scene-data.ts

@@ -90,7 +90,15 @@ function layersFromContents(contents: unknown[]): Layer[] {
 
 function parseScene(value: unknown): Scene | null {
   if (!isRecord(value)) return null;
-  if (typeof value.id !== "string") return null;
+  // Studio's own save format uses string ids; the V2 relational assembly uses numeric
+  // ids — accept both (coerce to string).
+  const id =
+    typeof value.id === "string"
+      ? value.id
+      : typeof value.id === "number"
+        ? String(value.id)
+        : null;
+  if (id === null) return null;
   const name =
     typeof value.name === "string"
       ? value.name
@@ -120,7 +128,7 @@ function parseScene(value: unknown): Scene | null {
       : "none";
 
   return {
-    id: value.id,
+    id,
     name,
     duration:
       typeof value.duration === "number"