docs: update page title to 'Updates, deletes and appends'

Renamed the pub/sub messages page from 'Updates and deletes' to
'Updates, deletes and appends' in both the navigation item and
page title to reflect the complete feature set.

https://claude.ai/code/session_011mir48T3KXQYTq1TLSdMs9

Author: claude

src/data/nav/pubsub.ts

@@ -195,7 +195,7 @@ export default {
           link: '/docs/messages/annotations',
         },
         {
-          name: 'Updates and deletes',
+          name: 'Updates, deletes and appends',
           link: '/docs/messages/updates-deletes',
         },
       ],

src/pages/docs/messages/updates-deletes.mdx

@@ -1,5 +1,5 @@
 ---
-title: Updating and deleting messages
+title: Updates, deletes and appends
 meta_description: "Update and delete messages published to a channel, and retrieve message version history."
 ---