Two new tools for efficient multi-file operations:
1. get_files_batch: Fetch up to 20 files in parallel via goroutines.
Replaces N individual get_file_contents calls.
Built-in safety cap on total response size (default 500KB).
2. commit_multiple_files: Atomic multi-file commit (create/update/delete).
Uses Gitea SDK ChangeFiles API. Max 50 files per commit.
Enables proper feature commits with single git history entry.
Both tools follow Security by Design: input validation, size limits,
proper error handling, no path traversal.
