feat(game): 结算倒计时展示+自动下一局

- 解析后端settlement_deadline_ms，展示5秒结算倒计时
- 下一局按钮显示倒计时秒数（如"下一局 (3s)"）
- 倒计时归零自动发送next_round（可提前点击）
- 新局开始时清除结算状态

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/views/ChengduGamePage.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import {computed, onBeforeUnmount, onMounted, ref} from 'vue'
+import {computed, onBeforeUnmount, onMounted, ref, watch} from 'vue'
 import {useRoute, useRouter} from 'vue-router'
 import deskImage from '../assets/images/desk/desk_01_1920_945.png'
 import robotIcon from '../assets/images/icons/robot.svg'
@@ -98,6 +98,7 @@ const discardPending = ref(false)
 const claimActionPending = ref(false)
 const turnActionPending = ref(false)
 const nextRoundPending = ref(false)
+const settlementDeadlineMs = ref<number | null>(null)
 const selectedDiscardTileId = ref<number | null>(null)
 let clockTimer: number | null = null
 let discardPendingTimer: number | null = null
@@ -352,6 +353,14 @@ const settlementPlayers = computed(() => {
       .sort((a, b) => b.score - a.score)
 })
 
+const settlementCountdown = computed(() => {
+  if (!showSettlementOverlay.value || !settlementDeadlineMs.value) {
+    return null
+  }
+  const remaining = Math.max(0, Math.ceil((settlementDeadlineMs.value - now.value) / 1000))
+  return remaining
+})
+
 const myReadyState = computed(() => {
   return Boolean(myPlayer.value?.isReady)
 })
@@ -1241,6 +1250,12 @@ function handleRoomStateResponse(message: unknown): void {
   if (typeof totalRounds === 'number') {
     gameStore.totalRounds = totalRounds
   }
+  const sdMs = readNumber(payload, 'settlement_deadline_ms', 'settlementDeadlineMs')
+  if (typeof sdMs === 'number' && sdMs > 0) {
+    settlementDeadlineMs.value = sdMs
+  } else if (phase !== 'settlement') {
+    settlementDeadlineMs.value = null
+  }
   gameStore.pendingClaim = normalizePendingClaim(payload)
   if (!gameStore.pendingClaim) {
     claimActionPending.value = false
@@ -1295,6 +1310,7 @@ function handleRoomStateResponse(message: unknown): void {
   }
   if (phase !== 'settlement') {
     nextRoundPending.value = false
+    settlementDeadlineMs.value = null
   }
   if (currentTurnPlayerId && currentTurnPlayerId !== loggedInUserId.value) {
     markDiscardCompleted()
@@ -1583,6 +1599,10 @@ function handleRoomInfoResponse(message: unknown): void {
   if (typeof infoTotalRounds === 'number') {
     gameStore.totalRounds = infoTotalRounds
   }
+  const infoSdMs = readNumber(gameState ?? {}, 'settlement_deadline_ms', 'settlementDeadlineMs')
+  if (typeof infoSdMs === 'number' && infoSdMs > 0) {
+    settlementDeadlineMs.value = infoSdMs
+  }
 
   setActiveRoom({
     roomId,
@@ -2753,6 +2773,12 @@ function hydrateFromActiveRoom(routeRoomId: string): void {
 }
 
 
+watch(settlementCountdown, (remaining) => {
+  if (remaining !== null && remaining <= 0 && !nextRoundPending.value && !isLastRound.value) {
+    nextRound()
+  }
+})
+
 onMounted(() => {
   const routeRoomId = typeof route.params.roomId === 'string' ? route.params.roomId : ''
   needsInitialRoomInfo = true
@@ -3161,7 +3187,9 @@ onBeforeUnmount(() => {
                     :disabled="nextRoundPending"
                     @click="nextRound"
                 >
-                  <span class="ready-toggle-label">{{ nextRoundPending ? '准备中...' : '下一局' }}</span>
+                  <span class="ready-toggle-label">
+                    {{ nextRoundPending ? '准备中...' : settlementCountdown != null && settlementCountdown > 0 ? `下一局 (${settlementCountdown}s)` : '下一局' }}
+                  </span>
                 </button>
                 <button
                     v-else