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/cards/test-echo.json

@@ -0,0 +1,23 @@
+{
+  "name": "Test Echo",
+  "type": "minion",
+  "cost": 1,
+  "attack": 1,
+  "health": 5,
+  "split": 1,
+  "text": [
+    {
+      "kind": "trigger",
+      "on": "anyMinionDamaged"
+    },
+    {
+      "kind": "effect",
+      "effect": {
+        "type": "dealDamage",
+        "target": "enemyHero",
+        "amount": 1
+      }
+    }
+  ],
+  "fictional": true
+}