Function truncate_display 

pub fn truncate_display(s: &str, max_chars: usize) -> String

Fixed-character truncation shared by every bounded-display projection this module (and its RPC callers, Phase 3 spec §3.1/§3.2) define — stated once so preview and commit always apply IDENTICAL bounds to the equivalent field, rather than independent per-endpoint copies drifting apart (the exact class of gap codex found and re-found across rounds 9 and 12).