refactor(map): 移除首波战斗倒计时相关逻辑

移除用于第一波战斗的倒计时功能，包括常量 BATTLE_COUNTDOWN_SECONDS 及相关方法 startBattleCountdownIfNeeded 和 finishBattleCountdown。同时清理了 waveSystemStart 中不必要的调度取消。

assets/script/game/map/MissionMonComp.ts

@@ -22,7 +22,6 @@ export class MissionMonCompComp extends CCComp {
     private static readonly MON_SLOT_START_X = 30;
     private static readonly MON_SLOT_X_INTERVAL = 60;
     private static readonly MON_DROP_HEIGHT = 280;
-    private static readonly BATTLE_COUNTDOWN_SECONDS = 3;
     @property({ tooltip: "是否启用调试日志" })
     private debugMode: boolean = false;
     @property({ tooltip: "每波基础普通怪数量" })
@@ -94,7 +93,6 @@ export class MissionMonCompComp extends CCComp {
         this.bossSpawnedInWave = false
         this.MonQueue = []
         this.resetSlotSpawnData()
-        this.unschedule(this.finishBattleCountdown)
         this.startNextWave()
         mLogger.log(this.debugMode, 'MissionMonComp', "[MissionMonComp] Starting Wave System");
     }
@@ -153,7 +151,6 @@ export class MissionMonCompComp extends CCComp {
         this.waveSpawnTimer = this.waveSpawnCd;
         this.nextAssignSlotIndex = 0;
         this.primeWaveInitialBurst();
-        this.startBattleCountdownIfNeeded();
         oops.message.dispatchEvent(GameEvent.NewWave, {
             wave: this.currentWave,
             total: this.waveTargetCount,
@@ -227,23 +224,6 @@ export class MissionMonCompComp extends CCComp {
         this.waveSpawnedCount += burstCount;
     }
 
-    private startBattleCountdownIfNeeded() {
-        if (this.currentWave !== 1) return;
-        smc.mission.pause = true;
-        smc.mission.stop_mon_action = true;
-        const dropDuration = Math.max(0.18, Math.min(0.38, MissionMonCompComp.MON_DROP_HEIGHT / 1200));
-        const lockDuration = dropDuration + MissionMonCompComp.BATTLE_COUNTDOWN_SECONDS;
-        this.unschedule(this.finishBattleCountdown);
-        this.scheduleOnce(this.finishBattleCountdown, lockDuration);
-    }
-
-    private finishBattleCountdown = () => {
-        if (!smc.mission.play) return;
-        if (!smc.mission.in_fight) return;
-        smc.mission.pause = false;
-        smc.mission.stop_mon_action = false;
-    }
-
     private resetSlotSpawnData() {
         this.slotSpawnQueues = Array.from(
             { length: MissionMonCompComp.MON_SLOT_COUNT },