test(@projects/@magic-civilization): 🐛 update stale Rust tests for DeclareWar action + player_index capping

- full_game_transcript: add the missing `Action::DeclareWar { target }` arm to the
  signature_of match (the tactical AI gained DeclareWar so AI-vs-AI leaves perpetual
  peace — non-exhaustive match broke compilation).
- ai_controller: player_index_to_slot now caps out-of-range indices to the last slot
  (graceful degradation for >MAX_PLAYERS games) instead of erroring; assert the cap.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/simulator/api-gdext/tests/ai_controller.rs

@@ -27,9 +27,13 @@ fn constructor_smoke_player_index_bounds() {
         player_index_to_slot((MAX_PLAYERS - 1) as i64).unwrap(),
         MAX_PLAYERS - 1
     );
-    assert!(
-        player_index_to_slot(MAX_PLAYERS as i64).is_err(),
-        "player_index >= MAX_PLAYERS must error"
+    // Out-of-range indices cap to the last slot (graceful degradation for games
+    // with more players than MAX_PLAYERS, e.g. the 5-clan demo) rather than
+    // erroring and taking no actions — see player_index_to_slot in ai.rs.
+    assert_eq!(
+        player_index_to_slot(MAX_PLAYERS as i64).unwrap(),
+        MAX_PLAYERS - 1,
+        "player_index >= MAX_PLAYERS must cap to the last slot"
     );
 }
 

src/simulator/crates/mc-player-api/tests/full_game_transcript.rs

@@ -1372,6 +1372,7 @@ fn ai_action_signature(action: &mc_ai::tactical::Action) -> String {
         A::DeploySiege { .. } => "deploy_siege".into(),
         A::PackSiege { .. } => "pack_siege".into(),
         A::Bombard { .. } => "bombard".into(),
+        A::DeclareWar { target } => format!("declare_war:{target}"),
     }
 }