codex: drop sitecustomize.py, setup.cfg, and the tracked .artifacts/

Coverage 7.7+ installs its own startup hook that honours
COVERAGE_PROCESS_START, so the repository sitecustomize.py duplicated it.
setup.cfg only redirected egg-info into .artifacts/, which in turn was
tracked (and shipped in the sdist) only so that directory existed; egg-info
now lands in the ignored repository root and .artifacts/ is ignored like
any other output directory. Three fewer entries in the root listing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: saidctb

.artifacts/.gitignore

@@ -11,6 +11,7 @@ mutants/
 .benchmarks/
 htmlcov/
 build/
+.artifacts/
 
 *.pyc
 *.pyo

.gitignore

@@ -7,6 +7,11 @@ release tags add a leading `v` to the package version.
 
 ## Unreleased
 
+- Local builds now write `prik.egg-info/` to the repository root, where Git
+  ignores it; `.artifacts/` still holds the documentation site and
+  distributions. Subprocess coverage uses the startup hook that ships with
+  coverage, so `COVERAGE_PROCESS_START` works as before.
+
 ## 0.5.1 — 2026-09-27
 
 ### Breaking changes

CHANGELOG.md

@@ -1,4 +1,3 @@
 include CHANGELOG.md
 include CITATION.cff
-include .artifacts/.gitignore
 recursive-include prik/cmake_modules *.cmake