fix(sidebar): 点击展开时文件树整体重建（两处根因）+ v0.24.1

用户报告：「点击展开的时候，文件树会频繁整体刷新，看起来非常难受」。

根因 1（主）：src/client/native/index.ts 的 sync() 把 files 接管项当成多余注册。
它按 KIND 记账、永远不在 wanted 里，于是每次 sync 都被 dispose + 重建；而
disposeSubscriptions 同时订阅了 service 与 store，**任何会话状态写入**（展开/收起、
切 tab、拖底部工作台、选中…）都会跑一遍 sync。替换 slot 注册 = 宿主换 slot entry →
插件 tab body 被 unmount/remount → 文件树丢失层缓存、滚动位置与目录 watcher，并重新
fs.trees([root, ...expanded]) 重列整棵可见树。机械证明（临时插桩，已回退）：
  [probe-sync] enter live=[editor,git,subagent,sidechat,diff,files]
  [probe-registerSlots] slot inject ran for dsh-better-sidebar:files
  [probe-body] unmount tab3 kind=files
  [probe-body] mount tab3 kind=files
修法：wantsFiles 提前，删除循环里对 files 接管项 skip（禁用 editor 时仍照旧释放）。

根因 2（次）：FileTree.tsx 的 retryDir 先把该层缓存删掉再请求，行被「Loading…」
占位替换后重建——目录有外部写入（构建 / 格式化 / 模型跑 bash）时整层闪空。
修法：复用既有 force 路径 loadLevels([dir], { force: true })，保留旧行直到新答案到达
（与 refreshTick 的强制刷新路径行为一致）。

判别性证据（回退任一修复即红）
- tests/native-surface.spec.ts：三次 store 写入不得产生任何注册/注销 → 回退后
  registered 6 → 12、disposed 全是 dsh-better-sidebar:files
- tests/file-tree-batch-load.spec.tsx：重列期间旧行仍在屏 → 回退后层被删空
- 新增真实宿主 lane tests/e2e/zz-expand-refresh.e2e.ts（quiescence 判据，无固定 sleep；
  zz- 前缀保证它最后跑，因为它会自建 workspace + session）：A1 展开只请求被展开那一层、
  A2 tab body 存活（不重开 watch socket）、A3 屏上行数不归零；回退修复 1 后退出码 1
  （Error: expanding a folder must ask for that folder, not the whole visible set）

修复后实测（40 子项目录，同一探针/机器/工作区）
| 阶段 | fs.trees payload | 新开 ws | DOM +/- | 被删行 | body 替换 | 层内最小行数 |
| 展开 big | [big]（原 [root, big]） | 0（原 1） | +41/-1 | 0（原 45） | 0（原是） | 40（原 40） |
| 外部写入 big | [big] | 0 | +1/-0（原 +41/-40） | 0 | 0 | 40（原 0） |
| 展开 bravo | [bravo] | 0 | +2/-1 | 0（原 45） | 0（原是） | 41 |

证伪记录：新建 fs.watch(dir,{persistent:false}) 在 macOS 上无改动时 0 事件（Node 微
探针两遍 + 8 轮真实时序 + 浏览器侧从未收到 {dir} 陈旧帧）→ src/fs-watch.ts 与
use-dir-watch.ts 一行未改。

验证：pnpm typecheck / lint / test（136 文件 1486 通过 9 跳过，基线 1484 + 新增 2）/ build
全绿；DSH_CMD='npx -y --package @deepseek-ai/dsh@0.2.0-rc.1 dsh' pnpm test:mount = 8/8。
版本 0.24.0 → 0.24.1（package.json / dsh.plugin.json / SIDEBAR_SERVICE_VERSION /
README×2 / CHANGELOG×2 同步）。

tests/native-surface.spec.ts

@@ -399,6 +399,73 @@ describe('registerNativeSurface lifecycle (service-driven registration)', () =>
     dispose()
   })
 
+  it('re-registers NOTHING on a store change (a folder toggle must not replace the explorer body)', () => {
+    // Regression (reported as "expanding a folder makes the whole tree
+    // refresh"): the surface kept its registrations in step by diffing them on
+    // every service AND store notification, and the built-in `files` takeover
+    // is keyed by its KIND — never by a descriptor id — so the "drop what is
+    // no longer wanted" loop read it as a stray registration and disposed it on
+    // EVERY state write. Disposing and re-creating a slot registration replaces
+    // the host's slot entry, which unmounts the tab body it draws: toggling a
+    // folder tore down the explorer (level cache, scroll position and the
+    // directory watcher all live in that component) and remounted it, so the
+    // tree blanked, re-requested [root, ...expanded] and rebuilt every row.
+    // The store notifies on each toggle, so this churned on every click.
+    const store = createSidebarStore()
+    store.setSession('s1')
+    const service = createBetterSidebarService(store)
+    service.registerTab({ id: 'editor', title: () => 'Files', component: () => null })
+    service.registerTab({ id: 'git', title: () => 'Changes', component: () => null })
+    const records = createNativeTabRecords()
+
+    /** Every slot registration, in order (the unregister keys land in `disposed`). */
+    const registered: string[] = []
+    const disposed: string[] = []
+    const registry = {
+      register: (definition: { id: string; kind: string; title: (address: string) => string }) =>
+        () => { disposed.push(definition.id) },
+    }
+    const ctx = {
+      inject: (_deps: readonly string[], callback: (injected: { get: (name: string) => unknown }) => void) => {
+        callback({ get: () => registry })
+        return { dispose: () => { /* the surface owns the rest */ } }
+      },
+      get: () => registry,
+      slots: {
+        inject: (_key: string, callback: () => () => void) => callback(),
+        register: (options: { name: string; key?: string }) => {
+          const key = options.key ?? options.name
+          registered.push(key)
+          return () => { disposed.push(key) }
+        },
+      },
+    }
+    const dispose = registerNativeSurface({ ctx: ctx as never, store, service, records })
+    const mounted = [...registered]
+    /** The takeover's slot registrations: its body + its chip title, one pair. */
+    const filesSlots = (): number => registered.filter(key => key === 'dsh-better-sidebar:files').length
+    expect(filesSlots(), 'the takeover registers its body + chip slots').toBe(2)
+    expect(disposed).toEqual([])
+
+    // A folder toggle: only state, no registry and no settings change. The
+    // native surface must not touch a single registration.
+    store.reduce(state => toggleExpanded(state, '/work/big'))
+    store.reduce(state => toggleExpanded(state, '/work/big/child'))
+    // Any other state write behaves the same (the workbench height, a tab
+    // switch, the selection — all of them notify the same subscribers).
+    store.update(state => { state.bottomOpen = !state.bottomOpen })
+    expect({ registered, disposed }).toEqual({ registered: mounted, disposed: [] })
+
+    // The takeover still follows the editor type's own switch: disabling the
+    // editor releases it, re-enabling brings it back exactly once.
+    store.setPrefs({ ...store.getPrefs(), tabsEnabled: { editor: false } })
+    expect(disposed).toContain('dsh-better-sidebar:files')
+    expect(registered).toEqual(mounted)
+    store.setPrefs({ ...store.getPrefs(), tabsEnabled: { editor: true } })
+    expect(filesSlots(), 'the re-enabled takeover registers again — exactly one pair').toBe(4)
+    dispose()
+  })
+
   it('claims exactly the extensions DSH has no preview for (the nine restored formats included)', () => {
     // DSH 0.1.7 handed every read-only preview to `ui-sidebar-documentpreview`,
     // and `canOpen` returning false is what gives the address away. The host's