chore: Support Poetry 2.3, fix broken peer deps

[GabDug]

Note

Low Risk
Primarily CI/tooling and documentation changes; main risk is CI environment resolution differences due to new version matrix entries and added dependency pins.

Overview
Updates the CI/tox test matrix to add Poetry 2.3 coverage (including GitHub Actions gh env mappings) and expands py314 Poetry runs accordingly.

Adjusts tox dependency constraints for PDM envs by pinning hishel<1.0 for PDM 2.21–2.25 to address broken/changed peer dependencies, and updates developer tooling by bumping .mise.toml to pdm 2.26 and configuring an auto-created .venv. Documentation is updated to state Poetry support up to 2.3+.

^{Written by Cursor Bugbot for commit 26a396e. This will update automatically on new commits. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.86%. Comparing base (2921303) to head (f978c5c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #68      +/-   ##
==========================================
- Coverage   97.14%   96.86%   -0.29%     
==========================================
  Files          12       12              
  Lines         701      701              
  Branches       63       63              
==========================================
- Hits          681      679       -2     
- Misses         18       19       +1     
- Partials        2        3       +1     

Flag	Coverage Δ
unittests	96.86% <ø> (-0.15%)	⬇️

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