Remove CLAUDE.md from version control

It's local AI-assistant guidance, not project documentation meant for
the repo. Kept on disk (gitignored) so it still works locally.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.gitignore

@@ -46,3 +46,6 @@ htmlcov/
 # Local Node artifacts used for tooling in this repo
 package.json
 package-lock.json
+
+# Local AI assistant instructions (not for the repo)
+CLAUDE.md