Sandbox gitconfig read-only; escape sequences preserved

What's Changed

• fix(sandbox): make ~/.gitconfig read-only in the macOS sandbox by @ompatel-aiml in https://github.com/google-gemini/gemini-cli/pull/28221
• fix(core): preserve escape sequences in string literals for modern models by @luisfelipe-alt in https://github.com/google-gemini/gemini-cli/pull/28299

Full Changelog: https://github.com/google-gemini/gemini-cli/compare/v0.51.0-nightly.20260706.gf7af4e518...v0.51.0-nightly.20260707.g15a9429b6