Move git utilities into a dedicated crate (#15564)

- create `codex-git-utils` and move the shared git helpers into it with
file moves preserved for diff readability
- move the `GitInfo` helpers out of `core` so stacked rollout work can
depend on the shared crate without carrying its own git info module

---------

Co-authored-by: Ahmed Ibrahim <219906144+aibrahim-oai@users.noreply.github.com>
Co-authored-by: Codex <noreply@openai.com>

codex-rs/core/src/config/mod.rs

@@ -39,7 +39,6 @@ use crate::config_loader::McpServerRequirement;
 use crate::config_loader::ResidencyRequirement;
 use crate::config_loader::Sourced;
 use crate::config_loader::load_config_layers_state;
-use crate::git_info::resolve_root_git_project_for_trust;
 use crate::memories::memory_root;
 use crate::model_provider_info::LEGACY_OLLAMA_CHAT_PROVIDER_ID;
 use crate::model_provider_info::LMSTUDIO_OSS_PROVIDER_ID;
@@ -66,6 +65,7 @@ use codex_features::FeatureConfigSource;
 use codex_features::FeatureOverrides;
 use codex_features::Features;
 use codex_features::FeaturesToml;
+use codex_git_utils::resolve_root_git_project_for_trust;
 use codex_protocol::config_types::AltScreenMode;
 use codex_protocol::config_types::ForcedLoginMethod;
 use codex_protocol::config_types::Personality;
@@ -134,7 +134,7 @@ pub use service::ConfigService;
 pub use service::ConfigServiceError;
 pub use types::ApprovalsReviewer;
 
-pub use codex_git::GhostSnapshotConfig;
+pub use codex_git_utils::GhostSnapshotConfig;
 
 /// Maximum number of bytes of the documentation that will be embedded. Larger
 /// files are *silently truncated* to this size so we do not take up too much of