fix: split long telegram final segments

[Shujakuinkuraudo]

Summary

• add a shared helper to split Telegram text by the 4096-character limit before sending
• reuse the helper for regular plain text sends and streaming final segments
• add regression tests for both Markdown and plain-text fallback paths

Problem

Telegram streaming replies could fail with Message is too long when the final accumulated segment exceeded Telegram's single-message limit.

The regular plain-text send path already split long messages, but _send_final_segment() still tried to send the whole final reply as one message. That made long streaming replies fail even though the adapter already had splitting logic available.

Testing

• ruff check astrbot/core/platform/sources/telegram/tg_event.py tests/test_telegram_adapter.py
• ruff format --check astrbot/core/platform/sources/telegram/tg_event.py tests/test_telegram_adapter.py
• pytest tests/test_telegram_adapter.py -q

Summary by Sourcery

Ensure Telegram text messages, including streaming final replies, are split according to Telegram’s length limit using a shared sending helper.

Bug Fixes:

• Prevent Telegram streaming final segments from failing when the accumulated reply exceeds the single-message length limit by splitting into multiple messages.

Enhancements:

• Introduce a shared helper to send long Telegram text messages with MarkdownV2 formatting and plain-text fallback, reused by both regular sends and streaming final segments.

Tests:

• Add regression tests to verify long Markdown-formatted final segments are split correctly and that plain-text fallback also splits correctly when Markdown conversion fails.

[sourcery-ai]

Hey - I've left some high level feedback:

• The test helpers _load_telegram_adapter and _load_telegram_platform_event duplicate the same mocked module setup; consider extracting a shared helper to build the patched sys.modules dict so future updates to the mock set don’t need to be made in multiple places.
• In test_telegram_final_segment_splits_long_plaintext_when_markdown_fails, reaching into event._send_final_segment.__func__.__globals__ to get telegramify_markdown is quite brittle; it would be more robust to patch the module at its import path (e.g., astrbot.core.platform.sources.telegram.tg_event.telegramify_markdown) so refactors to the method signature or scoping don’t silently break the test.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The test helpers `_load_telegram_adapter` and `_load_telegram_platform_event` duplicate the same mocked module setup; consider extracting a shared helper to build the patched `sys.modules` dict so future updates to the mock set don’t need to be made in multiple places.
- In `test_telegram_final_segment_splits_long_plaintext_when_markdown_fails`, reaching into `event._send_final_segment.__func__.__globals__` to get `telegramify_markdown` is quite brittle; it would be more robust to patch the module at its import path (e.g., `astrbot.core.platform.sources.telegram.tg_event.telegramify_markdown`) so refactors to the method signature or scoping don’t silently break the test.

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[gemini-code-assist]

Code Review

This pull request introduces a new helper method, _send_text_chunks, in astrbot/core/platform/sources/telegram/tg_event.py to centralize the logic for sending potentially long Telegram messages. This method handles text splitting, MarkdownV2 conversion, and gracefully falls back to plain text if Markdown conversion or sending fails. The existing send_with_client and _send_final_segment methods are refactored to utilize this new helper, reducing code duplication. Additionally, new tests have been added to tests/test_telegram_adapter.py to verify the message splitting and fallback behavior. A review comment suggests improving the exception handling in _send_text_chunks by catching more specific exceptions like ValueError and BadRequest instead of a broad Exception.