pysimlin: setuptools_scm fails on mcp-v0.1.4 git tag

[bpowers]

Problem

Building pysimlin fails because setuptools_scm picks up the mcp-v0.1.4 git tag and cannot parse it into a valid version for the pysimlin package. The error is:

tag 'mcp-v0.1.4' no version found
AssertionError in _parse_tag

setuptools_scm derives the package version from git tags, but mcp-v0.1.4 uses a component-prefixed tag format (mcp-v*) that does not match the version pattern expected by pysimlin's setuptools_scm configuration. Since mcp-v0.1.4 is the most recent tag reachable from HEAD, setuptools_scm selects it and fails.

Why it matters

This blocks the pre-commit hook for ALL commits. The hook runs pysimlin tests, which require building the package, and the build fails before any tests execute.

Component(s) affected

• src/pysimlin (setuptools_scm / pyproject.toml configuration)
• Pre-commit hook (scripts/pre-commit)

Possible approaches

1. Configure setuptools_scm with a tag_regex that only matches pysimlin-relevant tags (e.g., tags matching v* or pysimlin-v*, excluding mcp-v*).
2. Use setuptools_scm's git_describe_command option to pass --match patterns to git describe, so it only considers tags relevant to pysimlin.
3. Switch to a different versioning strategy for pysimlin (e.g., hardcoded version in pyproject.toml) if SCM-based versioning is not needed.

Option 1 or 2 is preferred since it preserves SCM-based versioning while filtering out unrelated component tags from the monorepo.

Context

Identified as a pre-existing infrastructure issue blocking the pre-commit hook for all commits. The mcp-v0.1.4 tag was created for the @simlin/mcp npm package and is unrelated to pysimlin.