organize MkDocs documentation

[laceyp99]

Summary

• organize the README content into a Material for MkDocs documentation site
• add focused getting-started, evaluation, analysis, development, and reference pages
• add Mermaid diagrams and document the docs dependency group and local preview workflow
• align AGENTS.md guidance with the new documentation structure

Testing

• uv run --locked --all-extras ruff format --check . - passed
• uv run --locked --all-extras ruff check . - passed
• uv run --locked --group docs mkdocs build --strict - passed
• uv run --locked --all-extras pytest -q - passed (130 tests)
• uv build - passed

[laceyp99]

Finally looks good to merge! After manual cleaning for readability and linking to relevant commands and repo docs, now the repo is representable.