Bug Description

When using streaming mode for Telegram replies, the first message sent via sendMessage may contain only 1-2 characters (e.g., "我" or "I"). Since iOS push notifications display the content of the first message, users see meaningless notifications.

Steps to Reproduce

1. Configure Telegram with streaming enabled (streamMode: partial or full)
2. Send a message that triggers a streaming response
3. Lock the phone and wait for push notification
4. Observe push notification content

Expected Behavior

Push notification should display meaningful content (e.g., the beginning of a sentence, at least 20-30 characters).

Actual Behavior

Push notification shows only 1-2 characters like "我" or "I" because the draft stream sends the first message immediately when any content is available.

Environment

• OS: iOS
• Channel: Telegram
• Stream mode: partial/full

Proposed Solution

Add a debounce mechanism to delay the first streaming message until it reaches a minimum character threshold (e.g., 30 chars). Short complete responses should still be sent immediately when streaming ends.