Skip non-package version files in wheels

[Sean-Kenneth-Doherty]

Fixes #1364

build_py should still write package-local generated version files into build_lib, because those files are importable package artifacts. But paths like a top-level VERSION file are source-tree artifacts; writing them into build_lib manufactures an installed wheel file that was not installed before.

This keeps source-tree generation unchanged, including SETUPTOOLS_SCM_WRITE_TO_SOURCE=1, but skips build outputs whose transformed path is outside discovered packages or declared py_modules.

I also included the minimal docs-environment fix needed for this PR to pass Read the Docs: the current mkdocstrings/pymdownx/Pygments stack crashes unless highlight titles are normalized, and the docs group now includes Ruff for signature formatting.

Tests:

• uv run --package setuptools-scm pytest setuptools-scm/testing_scm/test_integration.py::test_top_level_version_file_not_written_to_wheel setuptools-scm/testing_scm/test_integration.py::test_version_file_written_to_build_directory setuptools-scm/testing_scm/test_integration.py::test_version_file_src_layout_path_transformation -q
• TMPDIR=$PWD/.tmp PIP_CACHE_DIR=$PWD/.tmp/pip-cache uv run --package setuptools-scm pytest setuptools-scm/testing_scm/test_integration.py -q
• UV_PROJECT_ENVIRONMENT=$PWD/.tmp/rtd-venv uvx uv==0.11.14 sync --frozen --group docs && UV_PROJECT_ENVIRONMENT=$PWD/.tmp/rtd-venv uvx uv==0.11.14 run --no-sync --group docs python -m mkdocs build --clean --site-dir .tmp/rtd-site --config-file mkdocs.yml
• uv run --package setuptools-scm ruff check setuptools-scm/src/setuptools_scm/_integration/build_py.py setuptools-scm/testing_scm/test_integration.py --config setuptools-scm/pyproject.toml
• uv run --package setuptools-scm ruff format --check setuptools-scm/src/setuptools_scm/_integration/build_py.py setuptools-scm/testing_scm/test_integration.py --config setuptools-scm/pyproject.toml
• git diff --check

Prepared with local Codex assistance and reviewed/validated before submission.

[RonnyPfannschmidt]

closing as agentic abuse - the bot ignored prior discussion and prior work

the user was baned from pytest-dev for running unattended agents