Prepare v0.2.3 release materials

[HuRuilizhen]

Summary

This PR is the final v0.2.3 slice for release preparation.

The main goal is to update public-facing release materials after adding DeepSeek provider support and completing the local benchmark validation for the 0.2.3 LLM extraction enhancements.

Included

• refreshes the README for v0.2.3

  • adds deepseek to the documented provider list
  • documents DEEPSEEK_API_KEY
  • clarifies the narrower DeepSeek auto output-contract sequence:
    • json_object
    • prompt_only
  • updates the benchmark section to mention the current TechQA comparison set

• updates the public API notes for v0.2.3

  • adds deepseek to the supported provider set
  • documents the default DeepSeek base URL and API key environment variable
  • explains the DeepSeek-specific auto contract preference
  • keeps benchmark tooling clearly scoped to local development use

• prepares package metadata for release

  • bumps pyproject.toml from 0.2.2 to 0.2.3

Validation

Repository checks:

• .venv/bin/ruff check .
• .venv/bin/pyright
• .venv/bin/pytest -q

Build checks:

• .venv/bin/python -m build
• .venv/bin/python -m twine check dist/paralabelgen-0.2.3.tar.gz dist/paralabelgen-0.2.3-py3-none-any.whl

Example smoke tests:

• .venv/bin/python examples/basic_usage.py
• .venv/bin/python examples/custom_config.py
• .venv/bin/python examples/save_and_load.py

Notes

• this PR does not perform a local publish; the repository publish workflow remains tag-triggered
• local planning and evaluation documents under docs/ remain intentionally untracked and are not part of this branch