feat(email): document per-recipient best-effort delivery via failed

The email-send driver now attempts every recipient's private delivery
even when one fails, returning failed addresses in the result's
`failed` array instead of failing the whole call — so callers retry
only the failed subset and never re-mail delivered recipients. Adds
the field to the public EmailSendResult typing and module docs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/puter-js/src/modules/Email.js

@@ -27,6 +27,11 @@ import * as utils from '../lib/utils.js';
  * Recipients who unsubscribe are dropped from future sends — they come
  * back in the result's `suppressed` array — and a send whose `to` list
  * is entirely unsubscribed is rejected.
+ *
+ * Each recipient gets a private delivery. A recipient whose delivery
+ * fails comes back in the result's `failed` array (everyone else got
+ * their copy — retry with just those addresses); the call only rejects
+ * when no recipient could be delivered.
  */
 class Email {
     /**

src/puter-js/types/modules/email.d.ts

@@ -42,6 +42,12 @@ export interface EmailSendResult {
     cost: number;
     /** Recipients omitted because they opted out of this sender's mail. */
     suppressed: string[];
+    /**
+     * Recipients whose delivery attempt failed. Everyone else got their
+     * copy — retry with just these addresses. A send where every delivery
+     * fails rejects instead.
+     */
+    failed: string[];
 }
 
 /**