Fusion du lot G : sur une version retenue par une objection, « contre » et retrait oui, « pour » non (Yvv, 01/11)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ld-engine/src/objection.rs

@@ -17,6 +17,10 @@
 //!   is changed by a proposal. The target is fixed when the objection is raised;
 //! - the votes already cast on it stay, but it cannot enter into force
 //!   (`votable` and the adoption: a non-votable version is blocked);
+//! - while it is held, one may still **vote against it or take one's vote
+//!   back**, never add a *for* (`may_cast`, Yvv 2026-11-01: « Retirer ou
+//!   "contre" »): it can only lose votes, and once lifted it enters with the
+//!   votes still there;
 //! - its author **answers**: a substantive revision of it, or a proposal linked
 //!   to the objection (on the article it repeats, for a « redit »; a reworded
 //!   version, for a version without author). A substantive revision of **the
@@ -31,6 +35,7 @@
 //!   lift too (never reiterate: the objection is not theirs); withdrawing either
 //!   version ends it.
 
+use crate::ballot::Choice;
 use serde::{Deserialize, Serialize};
 use std::cmp::Ordering;
 
@@ -296,6 +301,16 @@ pub fn votable(id: &str, in_force: bool, held: &[&str]) -> bool {
     in_force || !held.contains(&id)
 }
 
+/// May this choice be cast on a version? `held` = a standing objection holds it
+/// back now (never a version in force, `votable`). Yvv, 2026-11-01, to « pendant
+/// qu'une objection retient une version, que permet-on ? »: « Retirer ou
+/// "contre" ». On a held version one may take one's vote back or vote against,
+/// never add a *for*: it can only lose votes while it is held, and once lifted it
+/// enters with the votes still there. A version not held takes any choice.
+pub fn may_cast(held: bool, choice: Choice) -> bool {
+    !held || choice != Choice::For
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -357,6 +372,17 @@ mod tests {
         assert!(votable("x", true, &["x"]), "a version in force is never made non-votable");
     }
 
+    #[test]
+    fn a_held_version_takes_against_and_withdrawal_never_for() {
+        // Yvv, 2026-11-01: « Retirer ou "contre" » — it can only lose votes while held.
+        assert!(!may_cast(true, Choice::For), "never a new *for* while held");
+        assert!(may_cast(true, Choice::Against), "against, yes");
+        assert!(may_cast(true, Choice::None), "taking one's vote back, yes");
+        for c in [Choice::For, Choice::Against, Choice::None] {
+            assert!(may_cast(false, c), "a version not held takes any choice: {c:?}");
+        }
+    }
+
     #[test]
     fn the_full_cycle_answer_reiterate_answer_lift() {
         let start = Phase::Author { cycle: 1 };