Fix parallel bot boat attacks of nations 🐛 (#4297)

## Description:

When a nation attacked multiple bots via boat attacks in parallel, each
boat attack computed its troop allocation independently using
`player.troops() / 5` without subtracting `botAttackTroopsSent`. The
cumulative troop commitment could exceed the nation's actual troop
count, and when the queued `AttackExecution`s ran `init()`, they drained
the nation to zero.

Planetary Realignment found this bug by accident, here Russia has only
39 troops:

<img width="1189" height="654" alt="image"
src="https://github.com/user-attachments/assets/07b85e00-6734-4ddd-a16e-fe53309e0ef8"
/>

The land attack path already handled this correctly. The bug in
`sendBoatAttack` was introduced by #3786, which made nations see and
attack enemies across rivers via boats, and changed `attackBots()` from
`.neighbors()` to `.nearby()`.

So the bug was on prod for the entirety of v31.

This fix extracts the shared attack troop calculation (reserve,
bot-aware allocation, troopSendCap, isAttackTooWeak, emoji) into a new
`calculateAttackTroops` method, with a callback for the non-bot troop
default (land: `player.troops() - targetTroops`, boat: `player.troops()
/ 5`). Bot targets in both paths now go through the same reserve-aware
calculation.

## Please complete the following:

- [X] I have added screenshots for all UI updates
- [X] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [X] I have added relevant tests to the test directory

## Please put your Discord username so you can be contacted if a bug or
regression is found:

FloPinguin

src/core/execution/utils/AiAttackBehavior.ts

@@ -927,7 +927,10 @@ export class AiAttackBehavior {
     return cap;
   }
 
-  private sendLandAttack(target: Player | TerraNullius): boolean {
+  private calculateAttackTroops(
+    target: Player | TerraNullius,
+    nonBotTroops: (targetTroops: number) => number,
+  ): number | null {
     const maxTroops = this.game.config().maxTroops(this.player);
     const botWithStructures =
       target.isPlayer() &&
@@ -950,7 +953,7 @@ export class AiAttackBehavior {
         this.player.troops() - targetTroops - this.botAttackTroopsSent,
       );
     } else {
-      troops = this.player.troops() - targetTroops;
+      troops = nonBotTroops(targetTroops);
     }
 
     // Hard & Impossible: don't drop below neighbor troop threshold (players only)
@@ -959,12 +962,12 @@ export class AiAttackBehavior {
     }
 
     if (troops < 1) {
-      return false;
+      return null;
     }
 
     // Hard & Impossible: don't attack if we'd send less than 20% of target's troops
     if (target.isPlayer() && this.isAttackTooWeak(troops, target)) {
-      return false;
+      return null;
     }
 
     if (target.isPlayer() && this.player.type() === PlayerType.Nation) {
@@ -972,6 +975,18 @@ export class AiAttackBehavior {
       this.emojiBehavior.maybeSendAttackEmoji(target);
     }
 
+    return troops;
+  }
+
+  private sendLandAttack(target: Player | TerraNullius): boolean {
+    const troops = this.calculateAttackTroops(
+      target,
+      (targetTroops) => this.player.troops() - targetTroops,
+    );
+    if (troops === null) {
+      return false;
+    }
+
     this.game.addExecution(
       new AttackExecution(
         troops,
@@ -1000,30 +1015,14 @@ export class AiAttackBehavior {
       return false;
     }
 
-    let troops;
+    const troops = this.calculateAttackTroops(
-    if (target.type() === PlayerType.Bot) {
+      target,
-      troops = this.calculateBotAttackTroops(target, this.player.troops() / 5);
+      () => this.player.troops() / 5,
-    } else {
+    );
-      troops = this.player.troops() / 5;
+    if (troops === null) {
-    }
-
-    // Hard & Impossible: don't drop below neighbor troop threshold
-    troops = Math.min(troops, this.troopSendCap());
-
-    if (troops < 1) {
       return false;
     }
 
-    // Hard & Impossible: don't attack if we'd send less than 20% of target's troops
-    if (this.isAttackTooWeak(troops, target)) {
-      return false;
-    }
-
-    if (target.isPlayer() && this.player.type() === PlayerType.Nation) {
-      if (this.emojiBehavior === undefined) throw new Error("not initialized");
-      this.emojiBehavior.maybeSendAttackEmoji(target);
-    }
-
     this.game.addExecution(
       new TransportShipExecution(this.player, closest.y, troops),
     );