Fix edge case in LaminarCurrentSourceDensity, use Poetry for builds, Python >= 3.10

[espenhgn]

Description

Updates LFPykit's packaging and CI to modern Python/PEP 517 tooling while fixing an edge case in LaminarCurrentSourceDensity that caused non-zero CSD sums in certain geometries.

Changes:

• Fix LaminarCurrentSourceDensity.get_transformation_matrix() fraction calculation when radius constraints are non-binding (z-plane crossing vs r–z intersection).
• Add Poetry-based pyproject.toml, remove legacy setup.py / setup.cfg, and bump version to 0.6.0 with Python >=3.10.
• Fix [tool.poetry.extras]: declare pytest, sympy, sphinx, numpydoc, sphinx_rtd_theme, and recommonmark as optional dependencies in [tool.poetry.dependencies] so that poetry install -E tests and poetry install -E docs work correctly, mirroring the old extras_require behavior from setup.py.
• Extend CI matrix to newer Python versions and add regression tests covering the edge case fix.

Related Issue

Motivation and Context

The LaminarCurrentSourceDensity class produced non-zero CSD sums in certain geometries due to an incorrect fraction calculation. The legacy setup.py-based packaging was replaced with a Poetry/PEP 517 setup for modern tooling support. The initial Poetry extras configuration was missing the required optional dependency declarations, preventing extras from being installable.

How Has This Been Tested

• Regression tests added covering the LaminarCurrentSourceDensity edge case.
• Poetry extras validated by ensuring all packages listed in [tool.poetry.extras] are declared as optional in [tool.poetry.dependencies].
• CI matrix extended to newer Python versions to verify compatibility.

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

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[Copilot]

Pull request overview

Updates LFPykit’s packaging and CI to modern Python/PEP 517 tooling while fixing an edge case in LaminarCurrentSourceDensity that caused non-zero CSD sums in certain geometries (Issue #196).

Changes:

• Fix LaminarCurrentSourceDensity.get_transformation_matrix() fraction calculation when radius constraints are non-binding (z-plane crossing vs r–z intersection).
• Add Poetry-based pyproject.toml, remove legacy setup.py / setup.cfg, and bump version to 0.6.0 with Python >=3.10.
• Extend CI matrix to newer Python versions and add regression tests covering Issue #196.

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
setup.py	Removed legacy setuptools build script in favor of PEP 517/Poetry.
setup.cfg	Removed legacy setuptools metadata config.
pyproject.toml	Introduces Poetry build configuration and dependency declarations.
lfpykit/version.py	Version bump to 0.6.0.
lfpykit/tests/test_module.py	Adds regression tests for Laminar CSD Issue #196; renames test ids for consistency.
lfpykit/models.py	Fixes Laminar CSD volume fraction calculation and simplifies _PrPz segment-hit logic.
.gitignore	Ignores macOS archive artifacts and an additional model directory.
.github/workflows/python-app.yml	Updates CI Python version matrix to 3.10–3.14.
.github/workflows/flake8.yml	Updates lint job Python version to 3.12.
.github/workflows/coveralls.yml	Updates coverage job Python version to 3.12.

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[torbjone]

I think this is ready to merge.