feat: multi-file edit support for apply_patch (Codex)

The apply_patch tool now accepts an `edits` array for batching
multiple file edits in a single call. Edits to the same file are
grouped into one *** Update File section with multiple @@ chunks,
sorted by line number for correct sequential application.

- Separate schemas: edit (single-file) vs apply_patch (multi-file)
- Separate descriptions per tool
- Hash invalidation tracks all edited files per patch

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