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

[vercel]

@lurenjia534 is attempting to deploy a commit to the Vercel Labs Team on Vercel.

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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.

[lurenjia534]

@visyat I resolved the merge conflict and pushed a follow-up fix for Telegram streaming segmentation.

The latest commit prevents streamed MarkdownV2 content from being truncated when the rendered Telegram payload grows beyond the original markdown source
length. I also added a regression test covering escaped MarkdownV2 expansion.

Verified locally:

• pnpm --filter @chat-adapter/telegram test
• pnpm check
• pnpm typecheck
• pnpm test:workspace
• pnpm build

Could you take another look when you have a chance?

[slmnsh]

Hi @visyat, any updates on this?

[vercel]

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Project	Deployment	Actions	Updated (UTC)
chat	Canceled	Open in v0	May 26, 2026 6:56am

[lurenjia534]

@visyat I synced the branch with the latest upstream main, including the CI Node version fix from #543.

I verified locally:

• pnpm --filter @chat-adapter/telegram test
• pnpm install --frozen-lockfile
• pnpm validate

All passed.

The current GitHub Actions CI run is action_required with no jobs started, so it looks like it needs maintainer
approval to run for this fork PR. The remaining Vercel failures are deployment authorization checks, not test
failures.