Publish API docs via pdoc and add docstrings

[nikhilvdev]

Add a GitHub Actions workflow (.github/workflows/docs.yml) to build and publish pdoc-generated API docs to GitHub Pages. Populate docstrings across the codebase (adapters, transports, plugins, CLI, formatter, worker, span, serverless, etc.) to produce a complete API reference; update README and CHANGELOG to advertise the docs and Kubernetes guidance. Expose CLI parser via build_parser for testing. Add a [docs] extra (pdoc) to pyproject.toml. Changes are documentation and docstring-focused; no functional behavior changes.

Summary

Checklist

• ruff check . passes
• mypy logquill passes (--strict on the public API)
• pytest passes, and new surface area has test coverage
• Public API additions are documented in README.md with a runnable example
• CHANGELOG.md has an entry under Unreleased
• If this touches the cross-language contract (levels, logger methods,
  record shape, transport/plugin contracts, config shape) shared with
  logquill-js, a matching tracking issue/PR is opened there

Scope