DX-1211: rewrite annotation missing-mode hint to split reject vs downgrade

The 93001 hint lumped two distinct failure modes under "if the subsequent
attach is rejected": a missing namespace rule (Mutable Messages) does reject
the attach, but a missing annotation-subscribe capability does NOT - the
server silently drops the mode and this same error re-fires. Confirmed by
live sandbox traces and the canonical error registry.

Reword to key off the symptom the caller observes: attach rejected => enable
the namespace rule; attach succeeds but annotations still undelivered =>
grant the capability. Addresses review feedback that the hint was
presumptuous and over-enumerated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: umair-ably

src/common/lib/client/realtimeannotations.ts

@@ -76,7 +76,7 @@ class RealtimeAnnotations {
           "You are trying to add an annotation listener, but you haven't requested the annotation_subscribe channel mode in ChannelOptions, so this won't do anything (we only deliver annotations to clients who have explicitly requested them)",
         code: 93001,
         statusCode: 400,
-        hint: 'Include "annotation_subscribe" in the channel modes: realtime.channels.get(name, { modes: ["subscribe", "annotation_subscribe", ...] }), or call channel.setOptions({ modes: [...] }) on an existing channel (this triggers a reattach). If the subsequent attach is rejected by the server, check that the channel namespace has "Message annotations, updates, and deletes" enabled in the Ably dashboard and that your API key has annotation-subscribe capability on this channel. If you have the Ably CLI installed, `ably apps rules list` shows which channel namespaces have Mutable Messages enabled, and `ably auth keys list` shows your key\'s capabilities.',
+        hint: 'Include "annotation_subscribe" in the channel modes: realtime.channels.get(name, { modes: ["annotation_subscribe", ...] }), or call channel.setOptions({ modes: [...] }) on an existing channel (this triggers a reattach). If the attach is then rejected, the channel namespace does not have "Message annotations, updates, and deletes" enabled (`ably apps rules list` shows which namespaces do). If the attach succeeds but annotations still are not delivered, your API key lacks the annotation-subscribe capability and the server silently dropped the mode (`ably auth keys list` shows your key\'s capabilities).',
       });
       Logger.logActionNoStrip(
         this.logger,