Open embed route to all origins, add embed snippet UI, enable LTspice

frame-ancestors * for /embed/* routes so any site can iframe notebooks.
Remove postMessage origin allowlist (theme toggle is cosmetic-only).
Add EmbedDialog popover with copy-paste iframe snippet and theme picker.
Enable ltspice in the engine dropdown now that the backend supports it.

frontend/src/components/embed/EmbedViewer.tsx

@@ -4,12 +4,6 @@ import * as api from '../../lib/api';
 import { EmbedCell } from './EmbedCell';
 import { Loader2 } from 'lucide-react';
 
-// Origins allowed to send postMessage theme changes to the embed.
-// Must stay in sync with CSP_FRAME_ANCESTORS / CORS_EXTRA_ORIGINS.
-const ALLOWED_MESSAGE_ORIGINS = new Set([
-  'https://forrest.warehack.ing',
-]);
-
 interface EmbedViewerProps {
   notebookId: string;
   initialTheme: string;
@@ -33,8 +27,6 @@ export default function EmbedViewer({ notebookId, initialTheme }: EmbedViewerPro
   // Listen for postMessage theme changes from parent iframe host
   useEffect(() => {
     function handleMessage(event: MessageEvent) {
-      if (!ALLOWED_MESSAGE_ORIGINS.has(event.origin)) return;
-
       if (event.data?.type === 'spicebook-theme') {
         const incoming = event.data.theme;
         if (incoming === 'dark' || incoming === 'light') {

frontend/src/components/notebook/toolbar/EmbedDialog.tsx

@@ -0,0 +1,97 @@
+import { useState, useRef } from 'react';
+import { Code, Check, Copy } from 'lucide-react';
+import { Popover, PopoverTrigger, PopoverContent } from '../../ui/popover';
+import { Button } from '../../ui/Button';
+import { useNotebookStore } from '../../../lib/notebook-store';
+
+export function EmbedDialog() {
+  const { notebookId } = useNotebookStore();
+  const [theme, setTheme] = useState<'dark' | 'light'>('dark');
+  const [copied, setCopied] = useState(false);
+  const timerRef = useRef<ReturnType<typeof setTimeout>>(undefined);
+
+  if (!notebookId) return null;
+
+  const origin = typeof window !== 'undefined' ? window.location.origin : '';
+
+  const snippet = `<iframe
+  src="${origin}/embed/${notebookId}?theme=${theme}"
+  width="100%" height="600"
+  style="border: 1px solid #334155; border-radius: 8px;"
+  allow="clipboard-write"
+></iframe>`;
+
+  function handleCopy() {
+    navigator.clipboard.writeText(snippet).then(() => {
+      setCopied(true);
+      clearTimeout(timerRef.current);
+      timerRef.current = setTimeout(() => setCopied(false), 2000);
+    });
+  }
+
+  return (
+    <Popover>
+      <PopoverTrigger asChild>
+        <Button variant="ghost" size="sm" title="Embed this notebook">
+          <Code className="w-3.5 h-3.5" />
+          Embed
+        </Button>
+      </PopoverTrigger>
+
+      <PopoverContent align="end" className="w-80">
+        <div className="space-y-3">
+          <p className="text-xs font-medium text-slate-300">
+            Embed this notebook on any page
+          </p>
+
+          {/* Theme toggle */}
+          <div className="flex gap-1 rounded-md bg-slate-800 p-0.5">
+            <button
+              onClick={() => setTheme('dark')}
+              className={`flex-1 rounded px-2 py-1 text-xs font-medium transition-colors ${
+                theme === 'dark'
+                  ? 'bg-slate-600 text-slate-100'
+                  : 'text-slate-400 hover:text-slate-300'
+              }`}
+            >
+              Dark
+            </button>
+            <button
+              onClick={() => setTheme('light')}
+              className={`flex-1 rounded px-2 py-1 text-xs font-medium transition-colors ${
+                theme === 'light'
+                  ? 'bg-slate-600 text-slate-100'
+                  : 'text-slate-400 hover:text-slate-300'
+              }`}
+            >
+              Light
+            </button>
+          </div>
+
+          {/* Snippet */}
+          <textarea
+            readOnly
+            value={snippet}
+            rows={5}
+            className="w-full resize-none rounded-md border border-slate-600 bg-slate-800 p-2 font-mono text-[11px] text-slate-300 focus:outline-none focus:border-blue-500"
+          />
+
+          {/* Copy button */}
+          <Button
+            variant="primary"
+            size="sm"
+            onClick={handleCopy}
+            className="w-full"
+          >
+            {copied ? (
+              <Check className="w-3.5 h-3.5" />
+            ) : (
+              <Copy className="w-3.5 h-3.5" />
+            )}
+            {copied ? 'Copied!' : 'Copy snippet'}
+          </Button>
+        </div>
+      </PopoverContent>
+    </Popover>
+  );
+}

frontend/src/components/notebook/toolbar/NotebookToolbar.tsx

@@ -12,6 +12,7 @@ import {
 import { Button } from '../../ui/Button';
 import { Badge } from '../../ui/Badge';
 import { Dropdown } from '../../ui/Dropdown';
+import { EmbedDialog } from './EmbedDialog';
 import { useNotebookStore } from '../../../lib/notebook-store';
 import type { CellType } from '../../../lib/types';
 
@@ -124,9 +125,7 @@ export function NotebookToolbar() {
           className="bg-slate-800 border border-slate-600 rounded text-xs px-2 py-1 text-slate-300 focus:outline-none focus:border-blue-500 cursor-pointer"
         >
           <option value="ngspice">ngspice</option>
-          <option value="ltspice" disabled>
-            ltspice (soon)
-          </option>
+          <option value="ltspice">ltspice</option>
         </select>
 
         {/* Dirty indicator */}
@@ -161,6 +160,9 @@ export function NotebookToolbar() {
           Run All
         </Button>
 
+        {/* Embed snippet */}
+        <EmbedDialog />
+
         {/* Save */}
         <Button
           variant={dirty ? 'primary' : 'ghost'}

frontend/src/middleware.ts

@@ -1,8 +1,8 @@
 import { defineMiddleware } from 'astro:middleware';
 
 // CSP frame-ancestors: controls which origins can embed this site in an iframe.
-// Only applied to /embed/* routes (the main app doesn't need to be framed).
-const FRAME_ANCESTORS = "'self' https://forrest.warehack.ing";
+// /embed/* routes allow framing from any origin; the main app stays locked to 'self'.
+const FRAME_ANCESTORS = '*';
 
 export const onRequest = defineMiddleware(async ({ url }, next) => {
   const response = await next();