fix(docs): standardize account-email cookie name (#1041)

Read `last_arcade_account_email` (the name Identity UI actually sets and the
marketing-site navbar reads) instead of `last_arcadedev_account_email`, which
nothing in the org sets — so the cookie fallback that prefills the user's email
in code examples was effectively dead. Aligns docs with the rest of the stack.

Co-authored-by: Juan Ibarlucea <juanibarlucea@192.168.1.2>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: 3 people

app/_components/placeholder-replacer.tsx

@@ -12,7 +12,8 @@ export function PlaceholderReplacer() {
     // 2. If Ory email is available, use that (highest priority)
     // 3. If no Ory email but cookie exists, use cookie value
     // 4. Otherwise, use original placeholder
-    const getCookieEmail = () => getCookie("last_arcadedev_account_email");
+    // Canonical name set by Identity UI and read by the website navbar.
+    const getCookieEmail = () => getCookie("last_arcade_account_email");
 
     const replacement = loading
       ? "{arcade_user_id}" // Keep original while loading