Function internal_note_message 

pub fn internal_note_message(text: &str) -> Message

Build an internal_only system Message carrying context an approver (or, later, a policy gate) injected before a tool runs (#67).

internal_only keeps the note out of the user-facing surface while the model still sees it in the prompt — the approver’s constraint shapes the model’s reasoning without surfacing as chatter. Persisted to the eventlog like any output message, so it re-enters the transcript on every replay.