Parse custom emoji into RichText.textCustomEmoji when sending markdown
rich messages, and round-trip them through edit, copy, and paste using a
shared tg://emoji?id=<fileId> markdown-link marker.
- Send: rewrite each customEmoji input attribute into a
[<alt>](tg://emoji?id=<fileId>) marker before the CommonMark parse, then
intercept the marker URL afterward to emit .textCustomEmoji. Only rich
messages are affected; a custom emoji alone stays on the entity path.
- Reverse: InstantPageToMarkdown (whole-message copy + edit reconstruction)
and InstantPageMultiTextAdapter (selection copy) emit the marker;
edit-load and chat paste reattach it as a live customEmoji attribute.
- Marker helpers shared in TextFormat/CustomEmojiMarkdownMarker.swift.
- Rich sends now pass inlineStickers so recipients can fetch the files.
Follow-up to verify at runtime: recipient rendering goes out with
Api.InputRichMessage.documents: nil; if recipients see only the fallback
glyph, populate documents: in apiInputRichMessage().
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
