Implement the nine message-entity RichText cases (textMention,
textMentionName, textHashtag, textCashtag, textBotCommand, textBankCard,
textAutoUrl, textAutoEmail, textAutoPhone): model + Postbox coding,
FlatBuffers schema/codec, Api.RichText parsing/serialization (lossless),
InstantPage display attaching the matching TelegramTextAttributes keys, and
tap routing in the rich-data bubble mirroring ChatMessageTextBubbleContentNode.
mentionName display resolves via EnginePeer.Id (PeerId not in scope).
Also lets rich-data text selection reach a line's trailing edge and fixes
the date/status node positioning to match TextBubble.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
