Add Python 3.13 Support for Blender 5.1

[GoodPie]

Description

Added additional builds for Blender 5.1, adding support for Python 3.13 (keeping support for Python 3.11).

[Copilot]

Pull request overview

This PR updates the CD workflow to build, test, and package artifacts for Blender 5.1 by adding Python 3.13 alongside the existing Python 3.11 support.

Changes:

• Extend cibuildwheel builds to include CPython 3.13 wheels across Linux/macOS/Windows.
• Run Python unit tests on a matrix of Python 3.11 and 3.13.
• Package Blender extensions for both Blender 5.0 (cp311) and 5.1 (cp313), and adjust artifact naming/downloading accordingly.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The wheel filtering step doesn’t verify that all expected wheels for the selected Python tag/platforms were copied before packaging. Since setup_addon.py only checks for a non-empty wheels/ directory, this job could still build and upload an extension that’s missing one or more platform wheels (e.g., if a macOS/Windows wheel build/upload failed). Consider failing the job here by explicitly checking for the expected wheel files (based on the CIBW_BUILD targets) and exiting non-zero if any are missing, rather than proceeding to package an incomplete addon.

Suggested change

	mkdir -p wheels
	cp all-wheels/*${{ matrix.python-tag }}*.whl wheels/ || true
	echo "Filtered wheels for ${{ matrix.python-tag }}:"
	set -euo pipefail
	mkdir -p wheels
	PY_TAG="${{ matrix.python-tag }}"
	echo "Filtering wheels for Python tag: ${PY_TAG}"
	# Count wheels matching the Python tag in the source directory
	SRC_COUNT=$(ls all-wheels/*"${PY_TAG}"*.whl 2>/dev/null | wc -l || true)
	if [ "${SRC_COUNT}" -eq 0 ]; then
	echo "Error: No wheels found in all-wheels/ for Python tag '${PY_TAG}'."
	exit 1
	fi
	# Copy all matching wheels into the wheels directory
	cp all-wheels/*"${PY_TAG}"*.whl wheels/
	# Verify that all expected wheels were copied
	DST_COUNT=$(ls wheels/*"${PY_TAG}"*.whl 2>/dev/null | wc -l || true)
	if [ "${DST_COUNT}" -ne "${SRC_COUNT}" ]; then
	echo "Error: Expected ${SRC_COUNT} wheels for Python tag '${PY_TAG}', but found ${DST_COUNT} in wheels/."
	exit 1
	fi
	echo "Filtered wheels for ${PY_TAG}:"