feat: add commander_bonus weight to score_card()

Commanders get +5.0 priority in AI spell selection, making the
AI prioritize casting its commander when affordable.

src/commander_ai_lab/sim/rules.py

@@ -68,6 +68,8 @@ AI_DEFAULT_WEIGHTS: dict[str, float] = {
     "spell_enchantment": 3.0,
     "spell_flash": 2.0,
     "spell_cascade": 3.0,
+    # Commander bonus
+    "commander_bonus": 5.0,
 }
 
 
@@ -320,6 +322,10 @@ def score_card(
     if "search your library" in text:
         score += w.get("spell_search", 2.0)
 
+    # ── Commander bonus ──
+    if card.is_commander:
+        score += w.get("commander_bonus", 5.0)
+
     return score