feat: replacement effects in Module 4 (Armor absorption, Bolf Ramshield redirect)

Applying a Damage to one target now runs DAMAGE_STEPS = [redirect, armor]
first. A damageRedirect aura (Bolf Ramshield, fetched from the wiki) sends
damage meant for its owner's hero to the oldest such minion; Armor absorbs
damage to a hero before Health, logged as the new ArmorLost{player, amount}
just before a full-amount Damaged. Four new Module 4 tests; propagated to the
references of Modules 4-10 in both tracks; card schema, catalog, card JSON,
harness.md, Lessons 2, 4 and 5 updated.

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

course/07-rule-resolution/reference/rust/src/engine/mod.rs

@@ -13,7 +13,8 @@
 //!
 //! Module 4: auras as card data, Aura Updates at defined points, and one
 //! routine that decides how many times a queued trigger activates. Playing a
-//! minion from hand, and Battlecries.
+//! minion from hand, and Battlecries. A second interceptor, replacement: the
+//! steps that rewrite a Damage before it lands (a redirect, then Armor).
 //!
 //! Module 5: behaviour as data. Cards are definitions in the course's card format,
 //! loaded from JSON; one interpreter turns their effects into actions. Assemble
@@ -36,9 +37,9 @@ mod world;
 
 pub use assemble::{assemble, register_assembled, AssembleError, Half};
 pub use card::{
-    Aura, Card, CardDef, CardLibrary, CardType, Clause, Effect, PoolFilter, Stacking, Target,
-    Trigger, TriggerOn,
+    Aura, Card, CardDef, CardLibrary, CardType, Clause, Effect, PoolFilter, RedirectFrom,
+    RedirectTo, Stacking, Target, Trigger, TriggerOn,
 };
 pub use event::Event;
-pub use queue::{run_sequence, summon, Action, Ctx};
+pub use queue::{run_sequence, summon, Action, Ctx, DamageStep, DAMAGE_STEPS};
 pub use world::{Chooser, EntityId, PlayerId, World, Zone, HERO_HEALTH};