Function noop_roundtrip_holds 

pub fn noop_roundtrip_holds(
    cx: &mut Cx,
    codec: &dyn SurfaceCodec,
    value: &Expr,
) -> Result<bool>

The weaker no-op reversibility check: decoding a noop_intent proposes no change. True for any editor that honors cancel, so it cannot stand in for roundtrip_holds – keep both.