fix: gitignore – update CMakeLists.txt exception + ignore macOS duplicates

- Exception updated to match renamed CMakeLists.txt (capital M)
- Add "* 2.*" / "* 3.*" patterns to suppress iCloud Drive duplicate
  files (e.g. "clausen 2.hpp") from appearing in git status

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

code/.gitignore

@@ -14,6 +14,10 @@ deps/*
 !deps/single_includes/
 !deps/CMakeLists.txt
 
+# macOS iCloud Drive duplicates ("file 2.cpp", "file 2.hpp", …)
+* 2.*
+* 3.*
+
 
 bin