docs: 增加 useMonitorLive 设计与实现计划

Monitor 直播会话逻辑抽离。

docs/superpowers/plans/2026-08-28-use-monitor-live.md

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+# useMonitorLive Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** 抽出直播会话逻辑。
+
+**Spec:** `docs/superpowers/specs/2026-08-28-use-monitor-live-design.md`
+
+### Task 1
+
+Create `src/composables/useMonitorLive.js`；迁入 `live` reactive、`livePhaseText`、`canFullscreenLive`、`toggleLive`/`fullscreenLive`/`openLive`/`refreshPlayURL`/`scheduleLiveHeartbeat`/`closeLive`。
+
+注入：`getDockId`（或 `getRecord`+推导）、`ui`、`getLivePlayer`。
+
+MonitorView 删除对应块；保留 `detailLiveView` computed 组装（可用 composable 返回值）；模板事件不变。
+
+Commit: `refactor: 抽取 useMonitorLive 直播会话逻辑`
+
+### Task 2 冒烟（Main）
+
+页面加载无 error；toggle 按钮存在；可 evaluate closeLive 无抛错。
+
+## 约束
+
+跳过全量测试；精确 git add；中文 commit

docs/superpowers/specs/2026-08-28-use-monitor-live-design.md

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+# useMonitorLive 设计
+
+## 目标
+
+抽出 Monitor 直播会话：`live` 状态、`openLive`/`closeLive`/`toggleLive`/`fullscreenLive`、heartbeat、playUrl 刷新与衍生文案。
+
+## 契约
+
+```js
+const {
+  live,
+  livePhaseText,
+  canFullscreenLive,
+  detailLiveView partial fields OR expose live + helpers,
+  toggleLive,
+  fullscreenLive,
+  closeLive,
+  openLive,
+} = useMonitorLive({
+  getDockId: () => /* 当前直播目标 dockId */,
+  ui,
+  getLivePlayer: () => detailPanelRef.value?.livePlayerRef,
+})
+```
+
+页面继续组装 `detailLiveView`（可把 phaseText/canFullscreen/playUrl 从 composable 取）。
+
+## 非目标
+
+- 不改 LivePlayer / API 形状
+- 不迁详情面板
+
+## 实现
+
+1. `src/composables/useMonitorLive.js`
+2. MonitorView 接线；`onUnmounted` 仍 `closeLive()`
+3. Commit: `refactor: 抽取 useMonitorLive 直播会话逻辑`
+
+## 约束
+
+精确 git add；中文 commit