feat: 计划模式 + 后续消息 + 会话分支接云端 (#65)

- 计划模式：tasks 加 plan 列；plan 与 approval=full / goal 冲突时
  400；执行器在 approval 参数后追加 --sandbox read-only（本地
  dispatch/run/goal/popen 与 Docker 内层命令全覆盖），host 任务
  存下 sandbox 后续轮次自动继承只读。
- 后续消息：新表 task_followups；POST/GET /tasks/{id}/followups
  （仅 queued/running 的非 goal 任务；direct 立即往链路追加
  phase=followup-direct 条目，本轮跑完后优先于排队执行；排队
  按 direct 优先、队内先来先服务逐条再跑一轮，同一 thread；
  一条失败即停、剩余 pending 留给重试入口；取消时回 pending）。
- 会话分支：POST /tasks/{id}/fork（仅终态任务；继承 executor/
  模型/强度/权限/计划，goal 字段置空）；worker 先 fork 再跑首轮，
  首轮失败不自动重试、不重复分叉，失败后走重试入口重跑首轮。
- 修任务级模型被覆盖：worker 此前无条件写成主模型，控制台
  选的模型实际不生效；现为任务级 > worker 主模型 > 配置。
- Docker 租户准备抽成 _docker_task_context，供普通尝试与 fork 共用。
- console：新建任务计划勾选（含冲突拦截）、详情计划徽标与
  分支来源、分支按钮与表单、后续消息区、列表 [计划]/[分支] 标记。
- 测试：cloud/tests/test_task_links.py 17 个（server 校验与继承、
  worker 模型优先、只读命令、排空顺序与停排、goal 不排空、
  fork 单次性）；全量 cloud 542、host 49、deploy 14。

Co-authored-by: host <host@test.local>

cloud/console.html

@@ -128,6 +128,7 @@
     <option value="cloud">cloud</option>
   </select>
   <label><input id="goalMode" type="checkbox"> goal 模式</label>
+  <label><input id="planMode" type="checkbox"> 计划模式（只读）</label>
 </div>
 <textarea id="prompt" placeholder="任务 prompt（必填）"></textarea>
 <div class="bar">
@@ -183,13 +184,28 @@
   <button id="btnCancel" class="danger">取消</button>
   <button id="btnMerge">合并（completed → merged）</button>
   <button id="btnPr">提 PR（须 merged）</button>
+  <button id="btnFork">分支</button>
   <button id="btnCost">查成本</button>
   <span id="actionMsg" class="muted"></span>
 </div>
+<div id="forkForm" style="display:none">
+  <input id="forkMsg" type="text" placeholder="分支首轮消息（必填，带历史的新会话）" style="width:100%; box-sizing:border-box; margin:6px 0;">
+  <div class="bar"><button id="btnForkConfirm" class="primary">创建分支任务</button><span id="forkMsgSpan" class="muted"></span></div>
+</div>
 <pre id="detailBody" style="display:none"></pre>
 <h3>实时链路</h3>
 <div id="traceBox" class="muted">点任务行查看详情后，这里显示过程链路</div>
 <div id="costBox"></div>
+<h3>后续消息</h3>
+<div id="followupForm">
+  <textarea id="followupText" placeholder="后续消息（任务运行中/排队中可用；排队不打断当前轮，直接发送跑完当前轮后优先执行）"></textarea>
+  <div class="bar">
+    <button id="btnQueueFollowup">排队</button>
+    <button id="btnDirectFollowup" class="primary">直接发送</button>
+    <span id="followupMsg" class="muted"></span>
+  </div>
+</div>
+<div id="followupList" class="muted"></div>
 </section>
 
 <script>
@@ -300,7 +316,7 @@ async function loadTasks() {
       var pr = t.pr_url ? "<a href='" + esc(t.pr_url) + "' target='_blank' rel='noopener'>#" + esc(t.pr_number) + "</a>" : "";
       return "<tr data-id='" + esc(t.id) + "' class='" + (currentTask && currentTask.id === t.id ? "selected" : "") + "'>" +
         "<td>" + esc(shortId(t.id)) + "</td>" +
-        "<td>" + esc(String(t.prompt || "").slice(0, 60)) + "</td>" +
+        "<td>" + (t.plan ? "[计划] " : "") + (t.forked_from ? "[分支] " : "") + esc(String(t.prompt || "").slice(0, 60)) + "</td>" +
         "<td class='st-" + esc(t.status) + "'>" + esc(t.status) + "</td>" +
         "<td>" + esc(t.executor || "") + "</td>" +
         "<td>" + esc(t.worktree_host || "") + "</td>" +
@@ -424,6 +440,8 @@ async function showDetail(taskId) {
       "executor " + esc(t.executor || "") + " ｜ 主机 " + esc(t.worktree_host || "") +
       " ｜ 模型 " + esc(t.model || "默认") + " ｜ 强度 " + esc(t.effort || "默认") +
       " ｜ 权限 " + esc(t.approval || "默认") +
+      (t.plan ? " ｜ <b>计划模式（只读）</b>" : "") +
+      (t.forked_from ? " ｜ 分支自 " + esc(shortId(t.forked_from)) : "") +
       (t.pr_url ? " ｜ <a href='" + esc(t.pr_url) + "' target='_blank' rel='noopener'>PR #" + esc(t.pr_number) + "</a>" : "") +
       "<br>prompt：<br>" + esc(t.prompt || "");
     var body = "";
@@ -434,9 +452,15 @@ async function showDetail(taskId) {
     pre.textContent = body;
     pre.style.display = "block";
     $("#detailActions").style.display = "flex";
+    $("#btnFork").style.display = TRACE_TERMINAL.indexOf(t.status) >= 0 ? "" : "none";
     $("#actionMsg").textContent = "";
     $("#costBox").innerHTML = "";
+    $("#forkForm").style.display = "none";
+    $("#forkMsgSpan").textContent = "";
+    $("#followupMsg").textContent = "";
+    $("#followupForm").style.display = ["queued", "running"].indexOf(t.status) >= 0 ? "block" : "none";
     startTrace(taskId, t.status);
+    loadFollowups(taskId);
   } catch (e) { $("#detail").innerHTML = "<span class='err'>加载失败：" + esc(e.message) + "</span>"; }
 }
 
@@ -452,6 +476,29 @@ async function doAction(kind) {
   } catch (e) { $("#actionMsg").innerHTML = "<span class='err'>" + kind + " 失败：" + esc(e.message) + "</span>"; }
 }
 
+async function loadFollowups(taskId) {
+  var box = $("#followupList");
+  try {
+    var d = await api("/tasks/" + encodeURIComponent(taskId) + "/followups", "GET");
+    var list = d.followups || [];
+    if (!list.length) { box.innerHTML = "（暂无后续消息）"; return; }
+    box.innerHTML = list.map(function (f) {
+      return "[" + esc(f.mode) + "｜" + esc(f.status) + "] " + esc(String(f.body || "").slice(0, 120));
+    }).join("<br>");
+  } catch (e) { box.innerHTML = "<span class='err'>后续消息加载失败：" + esc(e.message) + "</span>"; }
+}
+async function postFollowup(mode) {
+  if (!currentTask) return;
+  var text = $("#followupText").value.trim();
+  if (!text) { $("#followupMsg").textContent = "后续消息不能为空"; return; }
+  try {
+    await api("/tasks/" + encodeURIComponent(currentTask.id) + "/followups", "POST", { body: text, mode: mode });
+    $("#followupMsg").innerHTML = "<span class='ok'>已" + (mode === "direct" ? "直接发送" : "排队") + "</span>";
+    $("#followupText").value = "";
+    loadFollowups(currentTask.id);
+  } catch (e) { $("#followupMsg").innerHTML = "<span class='err'>发送失败：" + esc(e.message) + "</span>"; }
+}
+
 $("#saveKey").onclick = function () {
   var v = $("#key").value.trim();
   if (!v) { $("#keyState").textContent = "key 为空，未保存"; return; }
@@ -503,6 +550,11 @@ $("#createTask").onclick = async function () {
     if (ap === "full" && !confirm("完全访问 = 自动批准 + 不受工作区限制，agent 可读写工作区外路径。确认提交吗？")) return;
     body.approval = ap;
   }
+  if ($("#planMode").checked) {
+    if (ap === "full") { $("#taskMsg").textContent = "计划模式不能与完全访问同用"; return; }
+    if ($("#goalMode").checked) { $("#taskMsg").textContent = "计划模式不能与 goal 模式同用"; return; }
+    body.plan = 1;
+  }
   if ($("#goalMode").checked) {
     body.goal = $("#goal").value.trim() || prompt;
     body.verify_command = $("#verifyCommand").value.trim();
@@ -519,6 +571,24 @@ $("#btnRetry").onclick = function () { doAction("retry"); };
 $("#btnCancel").onclick = function () { doAction("cancel"); };
 $("#btnMerge").onclick = function () { doAction("merge"); };
 $("#btnPr").onclick = function () { doAction("pr"); };
+$("#btnFork").onclick = function () {
+  if (!currentTask) return;
+  if (TRACE_TERMINAL.indexOf(currentTask.status) < 0) { $("#forkMsgSpan").textContent = "仅终态任务可分支"; return; }
+  $("#forkForm").style.display = "block";
+};
+$("#btnForkConfirm").onclick = async function () {
+  if (!currentTask) return;
+  var msg = $("#forkMsg").value.trim();
+  if (!msg) { $("#forkMsgSpan").textContent = "分支消息必填"; return; }
+  try {
+    var t = await api("/tasks/" + encodeURIComponent(currentTask.id) + "/fork", "POST", { message: msg });
+    $("#forkMsgSpan").innerHTML = "<span class='ok'>分支任务已建：" + esc(shortId(t.id)) + "</span>";
+    $("#forkMsg").value = "";
+    loadTasks();
+  } catch (e) { $("#forkMsgSpan").innerHTML = "<span class='err'>分支失败：" + esc(e.message) + "</span>"; }
+};
+$("#btnQueueFollowup").onclick = function () { postFollowup("queued"); };
+$("#btnDirectFollowup").onclick = function () { postFollowup("direct"); };
 $("#btnCost").onclick = async function () {
   if (!currentTask) return;
   try {