Fix nations not spawning in singleplayer when player picks fast

NationExecution gated its first SpawnExecution by the same
attackRate/attackTick throttle used for AI actions, so a nation
could wait up to ~100 ticks before scheduling its spawn. In
singleplayer the human's spawn ends the spawn phase immediately,
stranding any nation that hadn't yet reached its attackTick — on
the next tick its NationExecution sees inSpawnPhase()=false and
isAlive()=false (no tiles), and deactivates itself.

First spawn now fires on tick 1, gated by a one-shot flag to
avoid queuing duplicates. The attackRate cadence is preserved for
subsequent re-spawns so nations still hop locations during the
spawn phase.

src/core/execution/NationExecution.ts

@@ -28,6 +28,7 @@ export class NationExecution implements Execution {
   private active = true;
   private random: PseudoRandom;
   private behaviorsInitialized = false;
+  private spawnExecAdded = false;
   private emojiBehavior!: NationEmojiBehavior;
   private mirvBehavior!: NationMIRVBehavior;
   private attackBehavior!: AiAttackBehavior;
@@ -104,7 +105,14 @@ export class NationExecution implements Execution {
     }
 
     if (this.mg.inSpawnPhase()) {
-      if (ticks % this.attackRate !== this.attackTick) {
+      if (this.player.hasSpawned()) {
+        // Already on the map — periodically re-spawn so the nation
+        // visibly hops to different locations during the spawn phase.
+        if (ticks % this.attackRate !== this.attackTick) {
+          return;
+        }
+      } else if (this.spawnExecAdded) {
+        // First SpawnExecution already queued, wait for it to land.
         return;
       }
       // Place nations without a spawn cell (Dynamically created for HumansVsNations) randomly by SpawnExecution
@@ -112,6 +120,7 @@ export class NationExecution implements Execution {
         this.mg.addExecution(
           new SpawnExecution(this.gameID, this.nation.playerInfo),
         );
+        this.spawnExecAdded = true;
         return;
       }
 
@@ -131,6 +140,7 @@ export class NationExecution implements Execution {
             this.mg.addExecution(
               new SpawnExecution(this.gameID, this.nation.playerInfo),
             );
+            this.spawnExecAdded = true;
             return;
           }
         }
@@ -147,6 +157,7 @@ export class NationExecution implements Execution {
       this.mg.addExecution(
         new SpawnExecution(this.gameID, this.nation.playerInfo, rl),
       );
+      this.spawnExecAdded = true;
       return;
     }