fix: make TDgpt model downloads fallback

[tomchon]

Summary

• Add a shared TDgpt Hugging Face download helper with correct boolean parsing and endpoint override support.
• Fall back from non-official endpoints such as hf-mirror.com to official Hugging Face when the first download attempt fails.
• Wire model_downloader.py and non-tdtsfm tsfmservice model servers to the helper, with focused tests for endpoint/fallback behavior.

Test Plan

• python3 -m pytest tools/tdgpt/tests/hf_download_test.py tools/tdgpt/tests/model_downloader_test.py -q
• python3 -m py_compile tools/tdgpt/taosanalytics/misc/hf_download.py tools/tdgpt/taosanalytics/misc/model_downloader.py tools/tdgpt/taosanalytics/tsfmservice/chronos-server.py tools/tdgpt/taosanalytics/tsfmservice/timemoe-server.py tools/tdgpt/taosanalytics/tsfmservice/timesfm-server.py tools/tdgpt/taosanalytics/tsfmservice/moirai-server.py tools/tdgpt/taosanalytics/tsfmservice/moment-server.py
• git diff --check

[gemini-code-assist]

Code Review

This pull request introduces a centralized Hugging Face model download utility with a fallback mechanism that reverts to the official endpoint if a mirror fails. It updates several service scripts and the model downloader CLI to utilize this new utility, while also improving boolean argument parsing and error handling. Review feedback highlights a logic error in is_official_endpoint regarding environment variable precedence and suggests removing endpoint from kwargs to avoid potential TypeError during the download call.

[Copilot]

Pull request overview

This PR improves reliability of TDgpt model downloads by introducing a shared Hugging Face download helper that supports endpoint overrides and automatic fallback to the official Hugging Face endpoint when a mirror/custom endpoint fails.

Changes:

• Added hf_download.py helper with robust boolean parsing, endpoint resolution, and mirror→official fallback logic.
• Updated model_downloader.py and multiple tsfmservice/*-server.py scripts to use the shared helper instead of directly calling huggingface_hub.snapshot_download.
• Added focused pytest coverage for endpoint resolution/fallback behavior and invalid CLI boolean handling.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
tools/tdgpt/taosanalytics/misc/hf_download.py	New shared helper for endpoint selection and fallback download behavior.
tools/tdgpt/taosanalytics/misc/model_downloader.py	Uses shared helper; fixes CLI boolean parsing + exit code.
tools/tdgpt/taosanalytics/tsfmservice/chronos-server.py	Switches model download to helper with fallback support.
tools/tdgpt/taosanalytics/tsfmservice/moirai-server.py	Switches model download to helper with fallback support.
tools/tdgpt/taosanalytics/tsfmservice/moment-server.py	Switches model download to helper with fallback support.
tools/tdgpt/taosanalytics/tsfmservice/timemoe-server.py	Switches model download to helper with fallback support.
tools/tdgpt/taosanalytics/tsfmservice/timesfm-server.py	Switches model download to helper with fallback support.
tools/tdgpt/tests/hf_download_test.py	New unit tests validating endpoint precedence and fallback behavior.
tools/tdgpt/tests/model_downloader_test.py	New test ensuring invalid boolean CLI arg exits cleanly.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.