feat: module 05 assemble

Cards become JSON data in course/cards (one file per card, validated
against card.schema.json and the catalog); the M5 references load them
via registerCards and interpret effects, replacing content closures.
Adds assemble(base, donor, half), the assemble/buffHand effects with an
injected chooser, Fleshshape as the data-only Expansion Drop, and stages
course/cards in verify-references and start-module.

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

course/05-assemble/reference/rust/src/engine/death.rs

@@ -0,0 +1,30 @@
+//! The Death Creation Step: the one place minions leave play.
+//!
+//! Damage and destroy effects only mark a minion (0 or less Health, or pending
+//! destroy). It stays in play, and keeps triggering, until the outermost Phase
+//! ends. Then this step removes every marked minion at once.
+
+use super::event::Event;
+use super::world::World;
+
+/// Remove every mortally wounded or pending-destroy minion from play, simultaneously.
+/// Returns their Death Events in order of play; empty if nothing died.
+pub fn death_creation_step(world: &mut World) -> Vec<Event> {
+    // Every position is read before anything moves: removal is simultaneous, and each
+    // Death Event remembers where its minion stood when the step began.
+    let mut deaths = Vec::new();
+    for id in world.minions_in_play() {
+        if world.is_doomed(id) {
+            let position = world
+                .board_index(id)
+                .expect("a minion in play is on the board");
+            deaths.push(Event::Destroyed { id, position });
+        }
+    }
+    for death in &deaths {
+        if let Event::Destroyed { id, position } = *death {
+            world.kill(id, position);
+        }
+    }
+    deaths
+}