Adds a new built-in module for Git operations using libgit2 (v1.9.0) statically linked.
Initial implementation includes Repository.open(), head(), and Commit properties (id, message, summary, author, committer, time).
Designed for local-only operations with lazy initialization to avoid overhead for users who don't need Git functionality.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
