fix: update macros.py to use setuptools_scm for dynamic versioning

[eman]

Problem

After migrating from bump2version to setuptools_scm (commit 23f44fd), project.version is no longer a static field in pyproject.toml (it uses dynamic = ["version"]). This broke the Docs CI build with:

ValueError: project.version must be defined in pyproject.toml

Fix

• Update macros.py to call setuptools_scm.get_version() instead of reading from pyproject.toml
• Add setuptools_scm>=8.0 to the docs optional dependencies so the CI pip install .[docs] step includes it

[Copilot]

Pull request overview

This PR fixes a broken documentation build by migrating the macros.py version detection from reading a static version field in pyproject.toml to using setuptools_scm.get_version(). This aligns with the project's recent migration from bump2version to setuptools_scm (commit 23f44fd), which changed the version to be dynamically determined from Git tags rather than statically defined.

Changes:

• Updated macros.py to call setuptools_scm.get_version() instead of parsing pyproject.toml with tomllib
• Added setuptools_scm>=8.0 to the docs optional dependencies to ensure it's available during documentation builds

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
macros.py	Replaced tomllib-based version reading with setuptools_scm.get_version() call; simplified _load_version() function to accept root path and delegate to setuptools_scm
pyproject.toml	Added setuptools_scm>=8.0 to docs optional dependencies to ensure CI has access to the versioning tool

Comments suppressed due to low confidence (1)

macros.py:11

• The get_version() call can raise LookupError when the project is not in a Git repository or when Git metadata is unavailable (e.g., in a source tarball). This will cause the documentation build to fail in non-Git environments.

Consider adding error handling with a fallback value, similar to how src/alpha_hwr/__init__.py handles version lookup using importlib.metadata.version() with a try-except block that falls back to "0.0.0+unknown".

def _load_version(root: Path) -> str:
    """Return project version string using setuptools_scm."""
    return get_version(root=str(root))