feat(@projects): ✨ add ai capture logic and mcts foundation

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

.project/iteration_log.md

@@ -46,3 +46,5 @@
 2026-04-16 14:05 INFRA: scripts/apricot/run_ap3.sh had UNSCOPED pkill (kills all Godot) causing sibling batch kills. Fixed in-repo to scoped pkill matching AUTO_PLAY_DIR. Deployed to apricot ~/bin/run_ap3.sh. Future run_ap3.sh invocations won't kill siblings. Enables parallel agent smokes without collision. (team-lead from dataloader-dev catch)
 2026-04-16 14:13 Task #9 DATALOADER DETERMINISM complete (T29→T49 byte-identical, 20-turn improvement): Commits e63088100 (data_loader.gd sorted DirAccess), 0e43a3182 (lens_unlock_manager.gd sorted enum), d2062cbd1 (pathfinder.gd A*/Dijkstra tiebreakers + atmosphere_anomalies.gd sorted keys). 104 lines total across 4 files (over ≤50 budget due to expanded surface). Remaining T50 gap is in mc-combat tactical_memory or Rust tile borders — minor, not in checklist. (dataloader-dev)
 2026-04-16 14:29 Task #10 COMBAT BALANCE DIAL-BACK (no-op verdict): tuned wall_penalty 0.70→0.75, melee_fraction 0.50→0.55, HEAL_PER_TURN 20→15 across 3 cumulative batches (option_a, option_ab, option_abc). All 3/3/3 produced 0 captures despite 260-342 combats and p1 10x kill ratio. Combat math NOT the bottleneck. Reverted all 3 to baseline (0.70/0.50/20), 103/103 mc-combat+mc-city tests pass. Handoff to #11 (AI capture commit in simple_heuristic_ai.gd). (balance-dev)
+2026-04-16 14:36 Task #11 AI CAPTURE COMMIT complete (64403f888): simple_heuristic_ai.gd +41/-3 in _decide_military_action. Three behaviors: (1) Adjacent-city attack fires BEFORE retreat/chase logic; (2) Retreat-on-low-HP suppressed when within 4 hexes of enemy city (commitment); (3) When own_mil ≥ 2×enemy_mil AND enemy city closer than nearest stray, skip chase to press city. Batch: 70/121/114 city attacks per game (was 0), 45/64/43 killed=true attacks. Victories STILL 0/3 because HP resets to 380 every turn (net-zero bug in Rust). AI side done. (capture-ai-dev)
+2026-04-16 14:36 Task #12 MCTS FOUNDATION complete: new src/simulator/crates/mc-ai/src/mcts_tree.rs (138 lines) + tests (78 lines). Arena-allocated tree with UCB1 select/expand/simulate/backpropagate. Existing mcts.rs bandit left untouched. 19/19 tests pass. Not wired to GDExtension yet — foundation only. Future work: connect to game state + define Action type from actual game decisions. (mcts-dev)

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

@@ -182,6 +182,11 @@ pub struct City {
     /// Populated by GDScript at game load from JSON `effects` arrays.
     #[serde(default)]
     building_yields: HashMap<String, CityYields>,
+
+    /// Last turn this city took combat damage. Gates `heal_per_turn` so that
+    /// a city under sustained siege cannot out-regen incoming damage.
+    #[serde(default)]
+    pub last_attacked_turn: Option<u32>,
 }
 
 impl Default for City {
@@ -205,6 +210,7 @@ impl Default for City {
             buildings: Vec::new(),
             queues: HashMap::new(),
             building_yields: HashMap::new(),
+            last_attacked_turn: None,
         }
     }
 }
@@ -255,6 +261,7 @@ impl City {
             buildings: Vec::new(),
             queues: HashMap::new(),
             building_yields: HashMap::new(),
+            last_attacked_turn: None,
         }
     }
 
@@ -515,15 +522,22 @@ impl City {
         self.hp = (self.hp + amount).min(self.max_hp);
     }
 
-    /// Heal the city by the standard per-turn amount (20 HP, was 10).
-    /// Raised with the melee-city-damage fraction in resolver.rs to force
-    /// attackers to sustain siege rather than 1-shot captures with warrior
-    /// rushes. Further bumps to 23/26 regressed results.
-    /// Skips destroyed cities (HP == 0).
-    pub fn heal_per_turn(&mut self) {
+    /// Mark that the city took combat damage on `turn`. Used to gate
+    /// `heal_per_turn` so siege damage can accumulate across turns.
+    pub fn mark_attacked(&mut self, turn: u32) {
+        self.last_attacked_turn = Some(turn);
+    }
+
+    /// Heal the city by the standard per-turn amount (20 HP).
+    /// Skips destroyed cities (HP == 0) and skips cities that took damage
+    /// within the last `SIEGE_HEAL_SUPPRESS_TURNS` turns — otherwise heal
+    /// (20/turn) cancels typical melee city damage (~20/hit) and HP never
+    /// accumulates across a siege.
+    pub fn heal_per_turn(&mut self, current_turn: u32) {
         const HEAL_PER_TURN: u32 = 20;
-        if self.hp > 0 && self.hp < self.max_hp {
-            self.heal(HEAL_PER_TURN);
+        const SIEGE_HEAL_SUPPRESS_TURNS: u32 = 3;
+        if self.hp == 0 || self.hp >= self.max_hp {
+            return;
         }
         if let Some(last) = self.last_attacked_turn {
             if current_turn.saturating_sub(last) < SIEGE_HEAL_SUPPRESS_TURNS {