feat(@projects/@magic-civilization): 🦌 p3-19 (core) — ecology population depletion API for player pressure

The Rust foundation for player→ecology feedback: PopulationSlot::deplete(amount)
(floors at 0, can cross the is_extinct threshold) + EcologyEngine::deplete_population
(col,row,species_id,amount) → post-depletion population, safe 0.0 no-op for a
missing tile/species. This is the hook hunting/harvesting will call to make
over-harvest drive local extinction; the engine's existing growth/emergence then
recovers abundance once pressure eases.

Tests: deplete_reduces_floors_at_zero_and_can_extinct (PopulationSlot) +
deplete_population_reduces_tile_species_and_can_extinct (engine); mc-ecology green.

p3-19 → partial. Remaining: GdEcologyEngine #[func] + GDScript kill/harvest wiring
+ dylib/GUT (loop continues).

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

.project/objectives/README.md

@@ -17,8 +17,8 @@
 | **P0** | 44 | 0 | 0 | 0 | 0 | 0 | 44 |
 | **P1** | 88 | 0 | 0 | 0 | 0 | 1 | 89 |
 | **P2** | 130 | 0 | 0 | 0 | 0 | 1 | 131 |
-| **P3 (oos)** | 30 | 0 | 3 | 0 | 2 | 29 | 64 |
-| **total** | **292** | **0** | **3** | **0** | **2** | **31** | **328** |
+| **P3 (oos)** | 30 | 0 | 4 | 0 | 1 | 29 | 64 |
+| **total** | **292** | **0** | **4** | **0** | **1** | **31** | **328** |
 
 </td><td valign='top' style='padding-left:2em'>
 

.project/objectives/p3-19-player-ecology-feedback.md

@@ -2,7 +2,7 @@
 id: p3-19
 title: Player → ecology feedback — harvesting & hunting deplete live populations (over-harvest → extinction)
 priority: p3
-status: missing
+status: partial
 scope: game1
 owner: warcouncil
 updated_at: 2026-06-25
@@ -24,6 +24,10 @@ Net: **you cannot over-harvest or over-hunt a species toward local extinction**,
 and abundance doesn't respond to player pressure — which undercuts the
 "living-world is the Game-1 USP" promise (the world should react to the player).
 
+## Progress (2026-06-25)
+
+Rust core landed: `PopulationSlot::deplete(amount)` + `EcologyEngine::deplete_population(col,row,species_id,amount)` (floors at 0, drives local extinction; missing tile/species = safe 0.0 no-op). Tests green (mc-ecology). **Remaining (the coupling/wiring):** a `GdEcologyEngine` `#[func]` exposing deplete + the GDScript kill (item_system.gd / lair clear) and intensive-harvest paths calling it for the victim/flora species at the tile + dylib rebuild + GUT proof that abundance responds to player pressure.
+
 ## Acceptance
 
 - [ ] Killing fauna (combat / lair clear) decrements that species' live

public/games/age-of-dwarves/data/objectives.json

@@ -1,10 +1,10 @@
 {
-  "generated_at": "2026-06-25T17:57:20Z",
+  "generated_at": "2026-06-25T18:06:31Z",
   "totals": {
-    "partial": 3,
     "in_progress": 0,
+    "missing": 1,
     "oos": 31,
-    "missing": 2,
+    "partial": 4,
     "stub": 0,
     "done": 292,
     "total": 328
@@ -3234,7 +3234,7 @@
       "id": "p3-19",
       "title": "Player → ecology feedback — harvesting & hunting deplete live populations (over-harvest → extinction)",
       "priority": "p3",
-      "status": "missing",
+      "status": "partial",
       "scope": "game1",
       "owner": "warcouncil",
       "updated_at": "2026-06-25",

src/simulator/crates/mc-ecology/src/engine.rs

@@ -269,6 +269,24 @@ impl EcologyEngine {
         self
     }
 
+    /// p3-19 — apply player pressure (hunting fauna / harvesting flora) to the
+    /// live population of `species_id` on tile `(col, row)`, reducing it by
+    /// `amount`. Returns the post-depletion population (`0.0` when the tile or
+    /// species has no slot). Sustained calls drive the slot to local extinction
+    /// ([`PopulationSlot::is_extinct`]); the per-turn growth/emergence dynamics
+    /// recover it once the pressure eases. This is the missing player→ecology
+    /// coupling — the engine already migrates/grows on its own, but nothing fed
+    /// player harvest/kills back into abundance.
+    pub fn deplete_population(&mut self, col: i32, row: i32, species_id: u32, amount: f32) -> f32 {
+        if let Some(slots) = self.tile_populations.get_mut(&(col, row)) {
+            if let Some(slot) = slots.iter_mut().find(|s| s.species_id == species_id) {
+                slot.deplete(amount);
+                return slot.population;
+            }
+        }
+        0.0
+    }
+
     /// Attempt to initialize GPU-accelerated population dynamics.
     ///
     /// Call after the grid is sized. If GPU hardware is unavailable or the tile
@@ -1354,6 +1372,24 @@ mod tests {
         );
     }
 
+    #[test]
+    fn deplete_population_reduces_tile_species_and_can_extinct() {
+        // p3-19: player pressure (hunt/harvest) on a tile's species reduces its
+        // live population and can drive local extinction; missing tile/species
+        // is a safe no-op returning 0.0.
+        let mut engine = EcologyEngine::new();
+        engine
+            .tile_populations
+            .insert((3, 4), vec![crate::population::PopulationSlot::new(7, 1.0)]);
+        let after = engine.deplete_population(3, 4, 7, 0.4);
+        assert!((after - 0.6).abs() < 1e-4, "0.4 depleted from 1.0");
+        let after2 = engine.deplete_population(3, 4, 7, 5.0);
+        assert_eq!(after2, 0.0, "over-depletion floors at 0");
+        assert!(engine.tile_populations[&(3, 4)][0].is_extinct());
+        assert_eq!(engine.deplete_population(9, 9, 7, 1.0), 0.0, "missing tile → 0");
+        assert_eq!(engine.deplete_population(3, 4, 999, 1.0), 0.0, "missing species → 0");
+    }
+
     #[test]
     fn full_cycle_with_predator_prey() {
         let mut grid = make_forest_grid(1, 1);

src/simulator/crates/mc-ecology/src/population.rs

@@ -35,6 +35,17 @@ impl PopulationSlot {
     pub fn is_extinct(&self) -> bool {
         self.population < 0.01
     }
+
+    /// p3-19 — reduce this population by `amount` from player pressure
+    /// (hunting fauna / harvesting flora), floored at 0. Sustained depletion can
+    /// push it below the [`Self::is_extinct`] threshold (local extinction); the
+    /// engine's growth/emergence dynamics let it recover once pressure eases.
+    /// Negative `amount` is ignored (use the normal growth path to add).
+    pub fn deplete(&mut self, amount: f32) {
+        if amount > 0.0 {
+            self.population = (self.population - amount).max(0.0);
+        }
+    }
 }
 
 #[cfg(test)]
@@ -56,4 +67,17 @@ mod tests {
         slot.population = 0.005;
         assert!(slot.is_extinct());
     }
+
+    #[test]
+    fn deplete_reduces_floors_at_zero_and_can_extinct() {
+        let mut slot = PopulationSlot::new(7, 1.0);
+        slot.deplete(0.3);
+        assert!((slot.population - 0.7).abs() < 1e-4, "0.3 depleted from 1.0");
+        assert!(!slot.is_extinct());
+        slot.deplete(5.0); // over-deplete floors at 0 → local extinction
+        assert_eq!(slot.population, 0.0);
+        assert!(slot.is_extinct(), "sustained over-harvest drives local extinction");
+        slot.deplete(-1.0); // negative ignored — growth uses the normal path
+        assert_eq!(slot.population, 0.0);
+    }
 }