Constant CAP_NOTICE_MARKER 

pub const CAP_NOTICE_MARKER: &str = "\n\n[supercode: tool output truncated — ";

Marker appended to a retained prefix when a runtime caps tool output.

This is owned by the reduction/rehydration contract because rehydration must recognize capped copies without depending on any particular agent runtime implementation. Runtime packages consume this marker when they create a capped view.