pub fn link_reply_to_fragment(
storage_root: &Path,
session_id: &str,
parent_fragment_id: &str,
reply_message_lamport: u64,
child_fragment_id: Option<&str>,
anchor_text: Option<&str>,
reply_text: Option<&str>,
branch_type_override: Option<&str>,
) -> Result<ChatGraphEdge, ChatError>