Function is_interruption_marker 

pub fn is_interruption_marker(text: &str) -> bool

True iff text is EXACTLY one of the interruption markers. Clients use this to render the marker as an “interrupted” line instead of a user bubble (the daemon’s DisplayItem has no dedicated variant: adding one would break older clients, whose DisplayItem has no #[serde(other)]). Exact, not a prefix: a user message that merely starts like a marker is the user’s, and is shown (and deduplicated) as such.