fix(hooks): add isGroup and groupId to message:sent context

Adds group context fields to MessageSentHookContext so hooks can
correlate sent events with received events for the same conversation.

Previously, message:received included isGroup/groupId but message:sent
did not, forcing hooks to use mismatched identifiers (e.g. groupId vs
numeric chat ID) when tracking conversations.

Fields are derived from MsgContext in dispatch-from-config and threaded
through route-reply and deliver via the mirror parameter.

Addresses feedback from matskevich (production user, 550+ events)
reported on PR #6797.

src/hooks/internal-hooks.ts

@@ -85,6 +85,10 @@ export type MessageSentHookContext = {
   conversationId?: string;
   /** Message ID returned by the provider */
   messageId?: string;
+  /** Whether this message was sent in a group/channel context */
+  isGroup?: boolean;
+  /** Group or channel identifier, if applicable */
+  groupId?: string;
 };
 
 export type MessageSentHookEvent = InternalHookEvent & {