Add Download button to in-play Scripts panel

Each script in the panel can now be downloaded as an import-compatible
JSON bundle (matching the /scripts export format), so demo/server-owned
scripts can be forked into a user's own library via the Scripts page's
Import.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TEpWMjnfPqzZ13nPMoGhs5

frontend/src/pages/Play.jsx

@@ -303,6 +303,22 @@ function ScriptsPanel({ advId }) {
     setScripts((prev) => prev.map((s) => (s.id === script.id ? updated : s)))
   }
 
+  // Download as an import-compatible bundle (matches /scripts export), so demo
+  // scripts can be forked into your own library via the Scripts page's Import.
+  const download = (s) => {
+    downloadJSON(
+      {
+        name: s.name,
+        description: s.description,
+        library: s.library_js,
+        input: s.input_js,
+        context: s.context_js,
+        output: s.output_js,
+      },
+      `${(s.name || 'script').replace(/\W+/g, '-')}.json`,
+    )
+  }
+
   if (!scripts) return <div className="empty">Loading…</div>
   if (scripts.length === 0) {
     return (
@@ -324,9 +340,12 @@ function ScriptsPanel({ advId }) {
                 <input type="checkbox" checked={s.enabled} onChange={() => toggle(s)} />
                 <span>{s.name}</span>
               </label>
+              <div style={{ display: 'flex', gap: 12, flexShrink: 0 }}>
                 <button className="linklike" onClick={() => setOpenId(open ? null : s.id)}>
                   {open ? 'Hide code' : 'View code'}
                 </button>
+                <button className="linklike" onClick={() => download(s)}>Download</button>
+              </div>
             </div>
             {s.description && <div className="dim adv-script-desc">{s.description}</div>}
             {open && (