fix(git): add offset_minutes to reflog entry for timezone-correct timestamps

CommitReflogEntry now includes offset_minutes field, populated from
sig.when().offset_minutes() — matches git's internal timezone offset
representation. Used by git_tools for accurate reflog timestamps.

libs/git/commit/meta.rs

@@ -121,6 +121,7 @@ impl GitDomain {
                     committer_name: sig.name().unwrap_or("").to_string(),
                     committer_email: sig.email().unwrap_or("").to_string(),
                     time_secs: sig.when().seconds(),
+                    offset_minutes: sig.when().offset_minutes(),
                     message: entry.message().map(String::from),
                     ref_name: refname.clone(),
                 });
@@ -207,6 +208,7 @@ impl GitDomain {
                 committer_name: sig.name().unwrap_or("").to_string(),
                 committer_email: sig.email().unwrap_or("").to_string(),
                 time_secs: sig.when().seconds(),
+                offset_minutes: sig.when().offset_minutes(),
                 message: entry.message().map(String::from),
                 ref_name: refname.clone(),
             });

libs/git/commit/types.rs

@@ -145,6 +145,7 @@ pub struct CommitReflogEntry {
     pub committer_name: String,
     pub committer_email: String,
     pub time_secs: i64,
+    pub offset_minutes: i32,
     pub message: Option<String>,
     pub ref_name: String,
 }