Move dev deps from extras to uv dependency groups

[PsiACE]

Changes Title (replace this with a logical title for your changes)

Description

Previously most developer/CI tooling lived in extras after #2085, which is not ideal since extras are for optional end‑user features.

This change migrates those dependencies to dependency groups and aligns tox, GitHub Actions, RTD, and docs with uv sync --group ..., removing requirements.txt usage in CI.

Status

Replace this: describe the PR status. Examples:

• done, ready for review

Checklist (tick everything that applies)

• Code linting (required, can be done after the PR checks)
• Documentation
• Tests
• ICLA (required for bigger changes)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.34%. Comparing base (909b8b0) to head (3e1f79b).

Additional details and impacted files

@@           Coverage Diff           @@
##            trunk    #2102   +/-   ##
=======================================
  Coverage   83.34%   83.34%           
=======================================
  Files         353      353           
  Lines       81769    81769           
  Branches     8993     8993           
=======================================
  Hits        68148    68148           
  Misses      10796    10796           
  Partials     2825     2825           

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