feat(telegram): add native DM draft streaming with segmented stream results

[lurenjia534]

Summary

Add native Telegram DM streaming via sendMessageDraft while preserving Chat SDK's existing post+edit fallback for non-DM threads.

This PR:

• adds native private-chat draft streaming to the Telegram adapter
• splits long streamed markdown into Telegram-safe persisted segments
• retries without parse_mode when Telegram rejects markdown entity parsing
• exposes segmented native stream results in the chat core
• updates docs and feature matrices to reflect Telegram DM draft streaming

Test plan

• pnpm check
• pnpm typecheck
• pnpm test:workspace
• pnpm build

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[lurenjia534]

Ah, I forgot to upload a video showing this PR

screen-20260407-075015-1775519367603-10mb.mp4

's effect it currently only works in private chats, since Telegram's official streaming API only allows us to use it in private conversations.