refactor(tasks): 移植主 Agent 同款合并活动折叠（数据层）

把上一轮验证过的数据层搬到工作图基座上，图/树两种模式共用：

- 新增 src/process-activity.ts：宿主 ui-chat 的 process group 算法移植
  （activity() 分类表逐条照抄、liveToolDetail 键优先级与 160 字截断、
  counts 计数排序与并列规则、preparing 语义、按 user/reply 边界切范围）。
  按本轮设计裁剪掉逐阶段列表（阶段改由徽标 + 颜色表达）。新增一条
  偏差：最新范围为空（子代理刚回复完）时回退到上一个「做过事」的范围，
  否则已结算卡片的小条只会显示「已完成分析」。
- chatT：从宿主 chat 命名空间读 message.stepProcess.* 措辞（方法调用 +
  try/catch 兜底，key 未命中即回退），4 个回归用例钉住「不许解绑 bind」。
- subagents.live 载荷换新：SidebarChildLiveView { running?, text?, summary?,
  lastEventTime? }，报告树内每个子节点（含已结算）与拓扑根；删除
  expand/stages 机制；childActivity → childLive（「不在 map 里 = 未运行」
  的读法随旧协议一起作废）。
- tasks-model 消费新形状；LiveLine 与节点详情浮窗改显示合并活动措辞。
- 删除 src/subagent-activity.ts 与 tests/subagent-activity.spec.ts。

验证：typecheck / lint 通过；pnpm test 1252 passed / 9 skipped。

(cherry picked from commit 5e5284f214846b0c366048acbee459f3a7a79456)

src/client/process-labels.ts

@@ -0,0 +1,115 @@
+/**
+ * The two labels the Tasks page borrows from the main conversation's merged
+ * activity display: the LIVE line ("正在运行命令 · npm run build") and the
+ * DONE title for a settled range ("已读取文件、执行了命令").
+ *
+ * Both are ports of the host's own composition
+ * (`dsh-client-ui-chat`'s `ProcessGroupHeader` + `step-process.js`
+ * `processTitle`), reading the host's `chat` dictionary through
+ * {@link chatT} so the wording — and every language the host ships — matches
+ * what the main chat shows for the same work.
+ *
+ * The translator is injectable for tests; the default is the host bridge. When
+ * a key does not resolve (a host that renamed it, or a deployment where the
+ * chat target never mounted) the call answers undefined and the card falls
+ * back to the tool detail it already has, never to a raw `message.…` key.
+ */
+import type { ProcessActivitySummary } from '../process-activity.ts'
+import { chatT } from './locales.ts'
+
+/** A host-namespace translator; undefined means "this key is not available". */
+export type ChatTranslate = (key: string, params?: Record<string, string | number>) => string | undefined
+
+/** The host's `' · '` line separator (`message.turnProcess.separator`). */
+function separator(t: ChatTranslate): string {
+  return t('message.turnProcess.separator') ?? ' · '
+}
+
+/**
+ * The live line of one stage: the running category's `…ing` wording plus the
+ * running call's detail, or the "thinking" default while nothing is dispatched
+ * (exactly the host's `ProcessGroupHeader` label rule).
+ *
+ * @param summary - the newest stage's summary (absent while the child has none).
+ * @param t - host translator (defaults to the `chat` namespace bridge).
+ * @returns the line, or undefined when there is nothing to say.
+ */
+export function liveActivityLabel(
+  summary: ProcessActivitySummary | undefined,
+  t: ChatTranslate = chatT,
+): string | undefined {
+  const activity = summary?.running ?? 'thinking'
+  const preparing = summary?.preparing === true
+  // The host maps its `thinking` fallback onto `prepare.tools` (there is no
+  // `prepare.thinking` key).
+  const label = preparing
+    ? t(`message.stepProcess.prepare.${activity === 'thinking' ? 'tools' : activity}`)
+    : t(`message.stepProcess.${activity}`)
+  if (label === undefined) {
+    // No host wording for this category: the detail is the honest fallback.
+    return summary?.runningDetail === undefined || summary.runningDetail === ''
+      ? undefined
+      : summary.runningDetail
+  }
+  const detail = preparing ? '' : summary?.runningDetail ?? ''
+  return detail === '' ? label : `${label}${separator(t)}${detail}`
+}
+
+/**
+ * The last-resort activity text: the ranked categories spelled out as
+ * `kind ×count`. It keeps a card informative when the host's `chat` wording is
+ * unavailable (renamed keys, or a deployment where the chat target never
+ * mounted) without inventing a second vocabulary for the normal case — the
+ * category names are the host's own, and they are language-neutral.
+ *
+ * @param summary - a stage's summary.
+ * @returns the counts text, or undefined when the stage called nothing.
+ */
+export function activityCountsText(
+  summary: ProcessActivitySummary | undefined,
+): string | undefined {
+  const counts = summary?.counts ?? []
+  if (counts.length === 0) return undefined
+  return counts.map(entry => `${entry.kind} ×${entry.count}`).join(' · ')
+}
+
+/**
+ * The settled range's title: the top three categories' `done.*` wording joined
+ * the way the host joins it (two labels share the "已" prefix; more than three
+ * append the "等" suffix). Counts are never printed.
+ *
+ * @param summary - a stage's summary.
+ * @param t - host translator (defaults to the `chat` namespace bridge).
+ * @returns the title, or undefined when the host wording is unavailable.
+ */
+export function doneActivityTitle(
+  summary: ProcessActivitySummary | undefined,
+  t: ChatTranslate = chatT,
+): string | undefined {
+  const counts = summary?.counts ?? []
+  if (counts.length === 0) return t('message.stepProcess.done.thinking')
+  const labels: string[] = []
+  for (const { kind } of counts.slice(0, 3)) {
+    const label = t(`message.stepProcess.done.${kind}`)
+    if (label === undefined) return undefined
+    labels.push(label)
+  }
+  const first = labels[0]
+  if (first === undefined) return undefined
+  const second = labels[1]
+  if (second === undefined) return first
+  // The host lowercases every label after the first for latin languages; a
+  // Chinese label is unaffected by that.
+  const continuation = (label: string): string => label.charAt(0).toLowerCase() + label.slice(1)
+  if (labels.length === 2) {
+    const prefix = t('message.stepProcess.sharedPrefix') ?? ''
+    const stripped = prefix !== '' && first.startsWith(prefix) && second.startsWith(prefix)
+      ? second.slice(prefix.length)
+      : second
+    return t('message.stepProcess.joinTwo', { first, second: continuation(stripped) })
+      ?? `${first}${separator(t)}${continuation(stripped)}`
+  }
+  const joined = [first, ...labels.slice(1).map(continuation)].join(t('message.stepProcess.comma') ?? ', ')
+  if (counts.length > 3) return t('message.stepProcess.more', { title: joined }) ?? joined
+  return joined
+}