Summary

• document that commit attribution for generated git commit messages is gated by the codex_git_commit feature flag
• add an example config.toml snippet showing commit_attribution with [features].codex_git_commit = true
• update the config schema description so the reference docs explain that commit_attribution only takes effect when the feature is enabled

Fixes #19799.

Validation

• cargo run -p codex-core --bin codex-write-config-schema
• cargo test -p codex-config
• cargo test -p codex-features
• cargo fmt --check
• git diff --check

Notes

• cargo test -p codex-core config_schema_matches_fixture currently fails before reaching the schema test because core_test_support imports similar without a linked crate in this checkout. The narrower package checks above avoid that unrelated test-support build failure.