build: upgrade Sphinx 4→7, drop m2r2/recommonmark, Python 3.11+

[TimeToBuildBob]

Fixes #157.

Upgrades the docs build stack to work with Python 3.13, which removed imghdr (breaking Sphinx 4.x's epub builder and other internals).

Changes

• Sphinx 4.x → >=7.0 (resolves Python 3.13 incompatibility; resolves Pin Python version (or update Sphinx) #157)
• Drop m2r2 + recommonmark — both unmaintained and incompatible with Sphinx 7+. Replaced by myst-parser which already handles all Markdown needs
• Drop setuptools workaround (was only needed for m2r2 on Python 3.12+)
• myst-parser pinned to >=2.0 (explicit requirement for Sphinx 7+)
• sphinx_rtd_theme >=2.0, sphinx-tabs ^3.4, sphinx-click >=6.0
• Python constraint: ^3.8 → ^3.11
• .readthedocs.yml: python 3.11 → 3.13 (per Erik's preference)
• CI: actions/checkout@v2→v4, setup-python@v1→v5, python 3.12 → 3.13
• Regenerated poetry.lock (sphinx 9.0.4, myst-parser 5.0.0)

conf.py

Replaced "m2r2" extension with "myst_parser". The .md files in changelog/ have corresponding .rst counterparts which are what's actually included — no functional change.

---

Important

Upgrade Sphinx to >=7.0, replace unmaintained dependencies, and update configurations for Python 3.13 compatibility.

• Dependencies:
  • Upgrade Sphinx from 4.x to >=7.0 in pyproject.toml.
  • Replace m2r2 and recommonmark with myst-parser >=2.0.
  • Update sphinx_rtd_theme to >=2.0, sphinx-tabs to ^3.4, and sphinx-click to >=6.0.
  • Remove setuptools workaround.
• Python Version:
  • Update Python constraint from ^3.8 to ^3.11 in pyproject.toml.
  • Change Python version to 3.13 in .readthedocs.yml and build.yml.
• CI/CD:
  • Update actions/checkout to v4 and setup-python to v5 in build.yml.
• Configuration:
  • Replace "m2r2" with "myst_parser" in conf.py.

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[TimeToBuildBob]

@greptileai review

[greptile-apps]

Greptile Summary

Upgraded documentation build stack to Sphinx 8.x for Python 3.13 compatibility, resolving the imghdr removal issue that broke Sphinx 4.x.

Key changes:

• Sphinx upgraded from 4.x to 8.x (constrained to <9 due to sphinx-tabs compatibility issue)
• Replaced unmaintained m2r2 and recommonmark with myst-parser >=2.0
• Updated all Sphinx extensions to compatible versions (sphinx_rtd_theme >=2.0, sphinx-tabs ^3.4, sphinx-click >=6.0)
• Python constraint changed from ^3.8 to ^3.11, with CI/ReadTheDocs using Python 3.13
• Fixed Sphinx 7+ configuration: added %s placeholders to extlinks, set language = "en", excluded duplicate changelog/*.md files
• Updated CI actions to latest versions (checkout@v4, setup-python@v5)

Confidence Score: 5/5

• This PR is safe to merge with no issues found
• All changes are well-coordinated across configuration files, dependency versions are properly constrained for compatibility, Sphinx 7+ configuration updates are correct, and the upgrade path addresses a real Python 3.13 compatibility issue. The PR went through multiple iterations to resolve compatibility issues (3 commits), demonstrating thorough testing.
• No files require special attention

Important Files Changed

Filename	Overview
pyproject.toml	Upgraded Sphinx to 8.x (constrained <9 for sphinx-tabs compatibility), replaced unmaintained m2r2/recommonmark with myst-parser, updated dependency versions, and changed Python constraint from ^3.8 to ^3.11
src/conf.py	Replaced m2r2 extension with myst_parser, fixed extlinks format for Sphinx 7+ (added %s placeholders), set language to "en", and excluded duplicate changelog/*.md files
.github/workflows/build.yml	Updated checkout action to v4, setup-python to v5, and Python version from 3.12 to 3.13
.readthedocs.yml	Updated Python version from 3.11 to 3.13 for ReadTheDocs build
poetry.lock	Regenerated lockfile with Sphinx 8.2.3, myst-parser 5.0.0, and updated transitive dependencies

_{Last reviewed commit: 537397c}

[greptile-apps]

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