fix: 调研/产品/UI 改为手动点击"开始"触发计时

去掉"到了计划日期自动变进行中"的逻辑，改为用户手动点击：
- pending 状态显示蓝色"开始"按钮
- 点击后记录 actualStartAt（精确时间戳）
- 进行中才显示"完成"按钮

跟开发/测试逻辑一致：状态由用户主动触发，时间戳准确。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/components/version/PlanTab.tsx

@@ -1,7 +1,7 @@
 'use client';
 
 import { useState } from 'react';
-import { Plus, Pencil, Trash2, X, Check, ExternalLink, FileUp, Link2 } from 'lucide-react';
+import { Plus, Pencil, Trash2, X, Check, ExternalLink, FileUp, Link2, Play } from 'lucide-react';
 import type { VersionPlan, PlanTask } from '@/lib/version-plan';
 import { calcPlanDuration, formatDuration, calcTotalDuration, calcPlanProgress, calcLinkedReqProgress } from '@/lib/version-plan';
 
@@ -56,19 +56,11 @@ export function PlanTab({ plans, versionId, versionDeadline, currentUserName, pl
         <div className="space-y-3">
           {typePlans.map((plan) => {
             const now = new Date().toISOString();
-            const nowDate = now.slice(0, 10);
-            // 自动进入进行中（到了计划开始日期）
-            const shouldAutoStart = plan.status === 'pending' && plan.startTime <= nowDate;
-            if (shouldAutoStart && !plan.actualStartAt) {
-              onUpdate(plan.id, { status: 'in_progress' });
-            }
-            const effectiveStatus = shouldAutoStart ? 'in_progress' : plan.status;
             // 耗时用实际时间戳计算
-            const actualStart = plan.actualStartAt || (shouldAutoStart ? now : null);
-            const dur = effectiveStatus === 'completed' && plan.completedAt && actualStart
-              ? calcPlanDuration(actualStart, plan.completedAt)
-              : effectiveStatus === 'in_progress' && actualStart
-                ? calcPlanDuration(actualStart, now)
+            const dur = plan.status === 'completed' && plan.completedAt && plan.actualStartAt
+              ? calcPlanDuration(plan.actualStartAt, plan.completedAt)
+              : plan.status === 'in_progress' && plan.actualStartAt
+                ? calcPlanDuration(plan.actualStartAt, now)
                 : { days: 0, hours: 0 };
             const durText = dur.days > 0 || dur.hours > 0 ? formatDuration(dur.days, dur.hours) : '-';
             return (
@@ -77,8 +69,8 @@ export function PlanTab({ plans, versionId, versionDeadline, currentUserName, pl
                   <div className="flex-1">
                     <div className="flex items-center gap-2 mb-1.5">
                       <span className="text-[13px] font-medium text-[var(--ink)]">{plan.title}</span>
-                      <span className={`inline-flex items-center rounded-md px-2 py-0.5 text-[10px] font-medium border ${STATUS_STYLE[effectiveStatus]}`}>
-                        {STATUS_LABEL[effectiveStatus]}
+                      <span className={`inline-flex items-center rounded-md px-2 py-0.5 text-[10px] font-medium border ${STATUS_STYLE[plan.status]}`}>
+                        {STATUS_LABEL[plan.status]}
                       </span>
                     </div>
                     <div className="flex items-center gap-4 text-[12px] text-[var(--ink-soft)]">
@@ -164,7 +156,7 @@ export function PlanTab({ plans, versionId, versionDeadline, currentUserName, pl
                             ) : null;
                           })}
                         </div>
-                        {calcLinkedReqProgress(plan.linkedRequirementIds, plan.completedRequirementIds) === 100 && effectiveStatus !== 'completed' && (
+                        {calcLinkedReqProgress(plan.linkedRequirementIds, plan.completedRequirementIds) === 100 && plan.status !== 'completed' && (
                           <div className="mt-2 rounded-lg bg-green-50 border border-green-200 px-3 py-2 flex items-center justify-between">
                             <span className="text-[12px] text-green-700">所有需求已完成，请提交原型成果</span>
                             <button onClick={() => setCompletingPlan(plan)} className="text-[11px] font-medium text-green-700 hover:text-green-900 underline">提交</button>
@@ -174,11 +166,18 @@ export function PlanTab({ plans, versionId, versionDeadline, currentUserName, pl
                     )}
                   </div>
                   <div className="flex items-center gap-1 ml-3">
-                    {effectiveStatus !== 'completed' && (
-                      <>
+                    {plan.status === 'pending' && (
+                      <button onClick={() => onUpdate(plan.id, { status: 'in_progress' })} className="h-7 px-2 flex items-center gap-1 rounded-md text-[11px] font-medium text-blue-600 hover:bg-blue-50 border border-blue-200" title="开始">
+                        <Play className="h-3 w-3" />开始
+                      </button>
+                    )}
+                    {plan.status !== 'completed' && plan.status !== 'pending' && (
                       <button onClick={() => setCompletingPlan(plan)} className="h-7 w-7 flex items-center justify-center rounded-md text-green-600 hover:bg-green-50" title="标记完成">
                         <Check className="h-3.5 w-3.5" />
                       </button>
+                    )}
+                    {plan.status !== 'completed' && (
+                      <>
                         <button onClick={() => setEditingPlan(plan)} className="h-7 w-7 flex items-center justify-center rounded-md text-[var(--ink-muted)] hover:bg-[var(--bg-subtle)]" title="编辑">
                           <Pencil className="h-3.5 w-3.5" />
                         </button>