feat: remove spawn timer on singleplayer (#3199)

Resolves #1041 

## Description:

Remove the singleplayer spawn countdown so the game starts when the
player spawns, spawn nations immediately after player spawn, and align
game timer/max-timer timing with the new start point.

Added a singleplayer regression test for spawn-immunity timing
(GameImpl.test.ts) and updated spawn-phase loop tests to use gameType:
GameType.Public where singleplayer behavior is not under test (e.g.
MIRV/AI/Spawn/WinCheck-related suites), eliminating inSpawnPhase()
timeout hangs after the new singleplayer start logic.


https://github.com/user-attachments/assets/c07a585f-1153-490e-88ca-a91fc7ae5756

## 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
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

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

tests/core/execution/SpawnExecution.test.ts

@@ -27,13 +27,11 @@ describe("Spawn execution", () => {
         spawnExecutions.push(new SpawnExecution("game_id", playerInfo));
       }
 
-      const game = await setup(mapName, undefined, players);
+      const game = await setup(mapName, {}, players);
 
       game.addExecution(...spawnExecutions);
-
-      while (game.inSpawnPhase()) {
-        game.executeNextTick();
-      }
+      game.executeNextTick();
+      game.executeNextTick();
 
       game.allPlayers().forEach((player) => {
         const spawnTile = player.spawnTile()!;
@@ -73,13 +71,11 @@ describe("Spawn execution", () => {
       spawnExecutions.push(new SpawnExecution("game_id", playerInfo));
     }
 
-    const game = await setup("half_land_half_ocean", undefined, players);
+    const game = await setup("half_land_half_ocean", {}, players);
 
     game.addExecution(...spawnExecutions);
-
-    while (game.inSpawnPhase()) {
-      game.executeNextTick();
-    }
+    game.executeNextTick();
+    game.executeNextTick();
 
     // Should spawn fewer than requested when map is too small
     expect(
@@ -96,14 +92,12 @@ describe("Spawn execution", () => {
       `player_id`,
     );
 
-    const game = await setup("half_land_half_ocean", undefined, [playerInfo]);
+    const game = await setup("half_land_half_ocean", {}, [playerInfo]);
 
     game.addExecution(new SpawnExecution("game_id", playerInfo, 10));
     game.addExecution(new SpawnExecution("game_id", playerInfo, 20));
-
-    while (game.inSpawnPhase()) {
-      game.executeNextTick();
-    }
+    game.executeNextTick();
+    game.executeNextTick();
 
     expect(game.playerByClientID("client_id")?.spawnTile()).toBe(20);
     // Previous territory from first spawn should be relinquished