Function agent_notes_since 

pub fn agent_notes_since(
    mem_name: &str,
    git_dir: &Path,
    since: &str,
    head_ref: Option<&str>,
) -> Result<AgentNotesReport, VcsError>

Walk the per-mem branch from since (exclusive) to the current branch tip (inclusive) and return one CommitNote per commit on the path, parsed via parse_commit_message. Order: newest first (matches git log default).

since may be the canonical empty-tree SHA — in which case every reachable commit is returned. Empty repos / empty refs return an empty report with head echoing the empty-tree sentinel.

head_ref follows the same convention as crate::ops::changes::changes_since: pass Some("refs/heads/<mem>") for mem-repo-backed mems, None to fall back to the gix HEAD.