Feature/thinkqe method

[haisonle001]

Summary

Adds a new thinkqe reformulation method to QueryGym.

Changes

• add querygym/methods/thinkqe.py
• add thinkqe.v1 prompt
• wire method exports/registration
• add ThinkQE docs and example config
• add unit tests for single-round and multi-round behavior
• Lint fix

Notes

• implementation follows the archive ThinkQE loop
• uses repeated chat() calls rather than chat_n
• supports archive-style params such as keep_passage_num, gen_num, num_interaction, accumulate, and use_passage_filter

Validation

• python -m py_compile querygym/methods/thinkqe.py querygym/core/runner.py querygym/__init__.py examples/querygym_pyserini/reformulate_queries.py
• python -m pytest -o addopts='' tests/test_method_thinkqe.py tests/test_methods_genqr.py tests/test_prompts.py