Add option (autoselect_llm) to automatically select the LLM

[dilithjay]

If parsing in AUTO-routing mode and autoselect_llm=True (can be set as a kwarg to the parse function)

A ranked list of models is obtained based on the similarity of the input doc to the documents in the benchmark. The model ranking for the most similar doc will be used for the input doc. The router will use the highest scoring model for which the API keys have been provided.

This PR also:

• Updates benchmark with autoselect_llm=True
• Refactors utility functions -> a separate file for conversion utils

[Copilot]

Pull Request Overview

This PR adds an automatic LLM selection feature for the parsing system. When autoselect_llm=True is set in AUTO-routing mode, the system selects the best-performing LLM based on document similarity to benchmark data.

• Introduces a new DocumentRankedLLMSelector that ranks models based on document similarity
• Refactors conversion utilities into a separate module for better organization
• Updates benchmark testing to support the new autoselect feature with comparative results

Reviewed Changes

Copilot reviewed 10 out of 15 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
lexoid/core/llm_selector.py	New module implementing document similarity-based LLM selection
lexoid/core/conversion_utils.py	Refactored conversion utilities moved from utils.py
lexoid/core/utils.py	Updated router function to support auto LLM selection and removed conversion functions
lexoid/core/parse_type/llm_parser.py	Updated imports and removed OpenAI parameter restrictions
lexoid/api.py	Modified parse function to handle auto-selected models
tests/benchmark.py	Added autoselect_llm parameter support and model name handling
tests/results.csv	Updated benchmark results including auto-selected model performance
tests/api_cost_mapping.json	Added cost mappings for GPT-5 models
docs/benchmark.rst	Updated documentation with new benchmark results
README.md	Updated benchmark table with latest performance data

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}