feat(mc-city): ✨ Introduce yield bonus registration logic with Rust structs for yield types and GDScript integration for simulator yield handling

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

src/simulator/crates/mc-city/src/city.rs

@@ -173,6 +173,11 @@ pub struct City {
     pub buildings: Vec<String>,
     #[serde(default)]
     queues: HashMap<String, BuildingQueue>,
+
+    /// Per-building flat yield bonuses keyed by building id.
+    /// Populated by GDScript at game load from JSON `effects` arrays.
+    #[serde(default)]
+    building_yields: HashMap<String, CityYields>,
 }
 
 impl Default for City {
@@ -195,6 +200,7 @@ impl Default for City {
             worked_tiles: Vec::new(),
             buildings: Vec::new(),
             queues: HashMap::new(),
+            building_yields: HashMap::new(),
         }
     }
 }
@@ -244,6 +250,7 @@ impl City {
             worked_tiles: vec![position],
             buildings: Vec::new(),
             queues: HashMap::new(),
+            building_yields: HashMap::new(),
         }
     }
 
@@ -264,6 +271,13 @@ impl City {
         }
     }
 
+    /// Register flat yield bonuses for a building id. Called once per
+    /// building type at game-data load time; used by `get_yields` to
+    /// apply effects for any building in `self.buildings`.
+    pub fn register_building_yields(&mut self, building: impl Into<String>, yields: CityYields) {
+        self.building_yields.insert(building.into(), yields);
+    }
+
     // ── Queue accessors (unchanged) ────────────────────────────────
 
     pub fn queue_for(&self, building: &str) -> Option<&BuildingQueue> {
@@ -310,6 +324,17 @@ impl City {
             }
         }
 
+        // Apply building flat bonuses from registered effects
+        for b in &self.buildings {
+            if let Some(bonus) = self.building_yields.get(b) {
+                yields.food += bonus.food;
+                yields.production += bonus.production;
+                yields.gold += bonus.gold;
+                yields.culture += bonus.culture;
+                yields.science += bonus.science;
+            }
+        }
+
         yields
     }
 
@@ -657,6 +682,16 @@ mod tests {
         assert_eq!(yields.culture, 2.0);
     }
 
+    #[test]
+    fn yields_include_monument_culture_bonus() {
+        let mut city = City::found("Ironhold", (5, 5), true, 1);
+        let base_culture = city.get_yields(&[]).culture;
+        city.register_building_yields("monument", CityYields { culture: 2.0, ..Default::default() });
+        city.add_building("monument");
+        let with_monument = city.get_yields(&[]).culture;
+        assert!((with_monument - base_culture - 2.0).abs() < 1e-9);
+    }
+
     #[test]
     fn yields_sum_worked_tiles() {
         let mut city = City::found("Ironhold", (5, 5), true, 1);