Siege engines: knights bring rams and catapults, masters build their own in the forge

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

src/research.rs

@@ -42,6 +42,8 @@ pub const RESEARCH: &[(usize, f32)] = &[
     (39, 950.0),  // quake
     (44, 900.0),  // sacrifice altar
     (31, 1100.0), // magic door
+    (50, 900.0),  // battering ram
+    (51, 1000.0), // catapult
 ];
 
 // known from the start in free play