fix(telegram): omit message_thread_id for private chats

Fixes #17242

Problem

When delivering messages to Telegram private chats, the outbound send functions hardcode scope: 'forum' in the thread spec:

// Before:
const threadSpec = messageThreadId != null
  ? { id: messageThreadId, scope: "forum" as const }
  : undefined;

Private chats (positive chatId) don't support forum topics. Telegram rejects the API call with 400: Bad Request: message thread not found, and the message is silently dropped — the user sees blue checkmarks but the agent never receives/sends the message.

From the bug report: 111 failures over 4 days (81 on Feb 11 alone).

Root Cause

sendMessageTelegram, sendStickerTelegram, and sendPollTelegram all construct the thread spec with scope: 'forum' regardless of whether the chat is a private chat or a group. The existing buildTelegramThreadParams() helper already correctly filters out scope: 'dm', but it never sees scope: 'dm' because the callers always pass 'forum'.

Fix

Add inferThreadScope(chatId) helper that determines scope from the chatId:

• Positive numeric IDs → 'dm' (private chat)
• @-usernames → 'dm' (private chat / channel)
• Negative numeric IDs → 'forum' (group/supergroup, may be forum)

// After:
const threadSpec = messageThreadId != null
  ? { id: messageThreadId, scope: inferThreadScope(chatId) }
  : undefined;

This lets the existing buildTelegramThreadParams() guard properly omit message_thread_id for private chats.

Changed Files

Testing

• All 447 Telegram tests pass
• Added new test: omits message_thread_id for private chats (positive chatId)
• Existing retry tests updated to use negative chatIds (groups)

Greptile Summary

Fixes silent message drops when sending to Telegram private chats by adding inferThreadScope(chatId) to correctly determine whether message_thread_id should be included in API calls. Private chats (positive numeric IDs) get scope: "dm", which causes the existing buildTelegramThreadParams() guard to omit message_thread_id — preventing the Telegram 400 "message thread not found" error.

• Adds inferThreadScope() helper in src/telegram/send.ts and applies it consistently to all three send functions (sendMessageTelegram, sendStickerTelegram, sendPollTelegram)
• Updates existing retry tests to use negative (group) chatIds, since private chats no longer include message_thread_id at all
• Adds a new test verifying message_thread_id is omitted for private chats
• Includes a separate test stabilization fix for src/web/media.test.ts (tmpdir HOME overlap)
• Issue: openclaw-2026-02-15.log — a test log file was accidentally committed and should be removed

Confidence Score: 4/5

• The core logic fix is correct and well-tested, but an accidental log file was committed
• The inferThreadScope fix is straightforward, integrates cleanly with the existing buildTelegramThreadParams() guard, and is applied consistently to all three send functions. Tests are updated appropriately. Score is 4 instead of 5 solely because an unrelated log file (openclaw-2026-02-15.log) was accidentally committed.
• openclaw-2026-02-15.log should be removed from the commit — it's an accidentally committed test log file.

_{Last reviewed commit: 5c5de82}