embed version in sdist and migrate to pyproject.toml

[branchvincent]

Fixes #29

Reading the version from the environment does introduce inconsistent versions, causing pip check to fail and even prevents uv from installing at all:

$ uv venv
$ uv pip install --no-binary=pycomposefile pycomposefile
  × Failed to download and build `pycomposefile==0.0.32`
  ╰─▶ Package metadata version `0.0.1a1` does not match given version `0.0.32`

Instead, this simply embeds the version in the sdist (example workflow run). Also, I took the opportunity to migrate to pyproject.toml, the modern replace for setup.py favoring static metatdata. To check the difference between the two builds:

$ uv build -o /tmp/before
$ git switch fix-version && uv build -o /tmp/after
$ uvx diffoscope --exclude-directory-metadata=recursive /tmp/before/*.tar.gz /tmp/after/*.tar.gz

[Copilot]

Pull Request Overview

This PR addresses version inconsistency issues by embedding the version directly in the sdist and modernizes the build configuration. The change fixes problems where dynamic version reading from environment variables caused pip check to fail and prevented uv from installing the package due to version mismatches.

• Migrates from setup.py to modern pyproject.toml configuration with static metadata
• Replaces dynamic environment-based versioning with sed-based version injection in CI
• Switches build system from setuptools to flit_core

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/setup.py	Removes legacy setuptools configuration file
src/pyproject.toml	Adds modern Python packaging configuration with static metadata
.github/workflows/publish.yaml	Updates CI to use sed for version injection instead of environment variables

[branchvincent]

hi @smurawski, should I fix the unrelated lint error in this PR? (might be good to add 3.13 to ci as well)

[usepowershell]

hi @smurawski, should I fix the unrelated lint error in this PR? (might be good to add 3.13 to ci as well)

That would be fantastic. Then I'll get this merged and shipped. Sorry for the delay in initially getting to this.

[branchvincent]

No worries, this should be ready now