Merge origin/main into refactor/issue-696-split-utils

Integrate #714 (show() decomposition) into the utils.py split. Only utils.py
conflicted:
- import block: dropped the now-unused `_locate_value` import (it moved to
  _color.py with the color code that uses it); kept main's `_locate_value`
  out of utils.
- `_fast_extent` docstring: took main's #714 version (D205 fix).

basic.py auto-merged: #714's decomposed show()/helpers now import color and
validation symbols from _color/_validate (the split's repoints), not utils.

Bonus: merging #714 brings its fixes for the pre-existing #703/#705 debt
(_resolve_measure_table str-return, _get_extent_fast Any-return, _fast_extent
D205), so the branch is now fully ruff + mypy clean (no --no-verify).

Verified: no import cycle; ruff + ruff-format + mypy all pass; 410 non-visual
tests pass.

Author: timtreis