fix(changes): 会话事件改走宿主 changes.ops 路由 + diff 展开二级设置 + 视觉迭代

CI 修复（plugin-mount 的 ctx.sessions.get TypeError ×1003）：
- 客户端 runtime 无事件日志面——badge/SessionLens 原在客户端直读
  ctx.sessions.get(id).events / ctx.on('session/event')，全部不可达。
- 新增宿主路由 changes.ops：live 会话日志优先，冷会话回放
  sessionPersistence.inspect；afterSeq 增量（缺省游标含 seq 0，
  显式游标为 seq > afterSeq，同 sidechat.events 约定），窗口上限
  4000 与客户端累加器一致。
- ChangesTab 轮询（mount 一拉 + visible 2.5s 增量）折入 ops，写
  模块级 opCounts 缓存供 badge 同步读取；SessionLens 改纯展示。

diff 展开二级设置（changesDiffFloat，默认浮窗）：
- prefs 四处接线 + git tab settings select（浮窗/面板，图标选项卡）
- 预览面板「展开为 diff tab」按设置落点：浮窗居中弹出或源 pane
  下方 split；i18n 全 21 词典同步。

视觉迭代（真机挂载截图审查后调整）：
- Session 视角：kind 徽章为左轨，大小+相对时间右对齐元列；失败
  操作行红色内嵌条；文件组头降为三级标签并加组间距。
- Git 视角：untracked '?' 徽章与新增同绿色；stage 按钮改 plus 图标。
- diff 折叠行：可展开折叠带 › 箭头 + 次级对比度，静态 gap 不再
  显示 pointer/hover；预览头路径改尾部截断（RTL 技巧，保文件名）。

验证：typecheck ✓ / vitest 1123 ✓ / pnpm test:mount（钉 alpha.2 CLI）
14/14 ✓；真机挂载截图（badge=5、双视角、浮窗展开）0 console error。

src/client/changes/SessionLens.tsx

@@ -1,62 +1,34 @@
 /**
  * The session lens of the changes tab: agent truth — every file the model
- * read, wrote, or edited in this session (folded from the session event
- * log), grouped by file, newest first, with kind filters. Clicking an op
- * previews it in the tab's shared bottom pane (see {@link DiffPane}): writes
- * and edits as line diffs, reads as a line-numbered content view, failures
- * as their real error text. Live `tool/call` / `tool/result` events append
- * while the tab is visible (bounded; paused and caught up when hidden).
+ * read, wrote, or edited in this session, grouped by file, newest first,
+ * with kind filters. Clicking an op previews it in the tab's shared bottom
+ * pane (see {@link DiffPane}): writes and edits as line diffs, reads as a
+ * line-numbered content view, failures as their real error text. The ops
+ * arrive pre-folded from the tab (which owns the event poll); this
+ * component is purely presentational.
  */
-import { useEffect, useMemo, useRef, useState, type ReactNode } from 'react'
-import type { SidebarSessionEvent } from '../../context-types.ts'
-import type { Context } from '../../context-types.ts'
-import type { SessionScope } from '../api.ts'
+import { useMemo, useState, type ReactNode } from 'react'
 import { relativeTime, t } from '../locales.ts'
-import { extractFileOps, groupByFile, knownContentBefore, type FileOp, type FileOpKind } from './ops.ts'
+import { groupByFile, type FileOp, type FileOpKind } from './ops.ts'
 import { formatBytes } from '../diff/rows.ts'
 import css from './changes.module.css'
 
-/** Cap on accumulated events: the lens shows the recent window, not eternity. */
-const EVENTS_CAP = 4000
-
 /** The op-kind filter chips: 'all' or one concrete kind. */
 type OpFilter = 'all' | FileOpKind
 
 export interface SessionLensProps {
-  ctx: Context
-  scope: SessionScope
-  /** Preview one op in the shared bottom pane (with its best-effort prior content). */
-  onPreview: (path: string, op: FileOp, prior: string | undefined) => void
+  /** The folded file operations, newest first (the tab's poll owns them). */
+  ops: readonly FileOp[]
+  /** Every poll failed and nothing loaded: an inline notice, not an empty
+   *  state that would read as "no operations". */
+  loadError: boolean
+  /** Preview one op in the shared bottom pane. */
+  onPreview: (path: string, op: FileOp) => void
   /** The op currently previewed (row highlight); null when the pane is closed. */
   selectedCallId: string | null
-  /** Fold events only while the tab is actually visible. */
-  visible: boolean
 }
 
-export function SessionLens({ ctx, scope, onPreview, selectedCallId, visible }: SessionLensProps) {
-  // The event log snapshot seeds the lens once; live tool/call and
-  // tool/result events append (bounded) and re-extract while visible.
-  const eventsRef = useRef<readonly SidebarSessionEvent[] | null>(null)
-  if (eventsRef.current === null) {
-    eventsRef.current = ctx.sessions.get(scope.sessionId)?.events ?? []
-  }
-  const [tick, setTick] = useState(0)
-  useEffect(() => {
-    if (typeof ctx.on !== 'function') return
-    const off = ctx.on('session/event', (session: unknown, event: SidebarSessionEvent) => {
-      const sessionId = (session as { id?: unknown } | null)?.id
-      if (sessionId !== scope.sessionId) return
-      if (event.type !== 'tool/call' && event.type !== 'tool/result') return
-      const list = [...eventsRef.current ?? [], event]
-      eventsRef.current = list.length > EVENTS_CAP ? list.slice(list.length - EVENTS_CAP) : list
-      if (visible) setTick(value => value + 1)
-    })
-    return () => { off() }
-  }, [ctx, scope.sessionId, visible])
-  // Becoming visible again catches up on events appended while paused.
-  useEffect(() => { if (visible) setTick(value => value + 1) }, [visible])
-
-  const ops = useMemo(() => extractFileOps(eventsRef.current ?? []), [tick])
+export function SessionLens({ ops, loadError, onPreview, selectedCallId }: SessionLensProps) {
   const [filter, setFilter] = useState<OpFilter>('all')
   const filteredOps = useMemo(
     () => (filter === 'all' ? ops : ops.filter(op => op.kind === filter)),
@@ -91,7 +63,8 @@ export function SessionLens({ ctx, scope, onPreview, selectedCallId, visible }:
         {chip('read', t('changesRead'), counts.get('read') ?? 0)}
       </div>
       <div className={css.sessionList}>
-        {ops.length === 0 && <div className={css.empty}>{t('changesSessionEmpty')}</div>}
+        {loadError && <div className={css.loadError}>{t('changesLoadError')}</div>}
+        {ops.length === 0 && !loadError && <div className={css.empty}>{t('changesSessionEmpty')}</div>}
         {ops.length > 0 && filteredOps.length === 0 && <div className={css.empty}>{t('changesFilterEmpty')}</div>}
         {[...groups.entries()].map(([path, fileOps]) => (
           <div key={path} className={css.fileGroup}>
@@ -104,19 +77,21 @@ export function SessionLens({ ctx, scope, onPreview, selectedCallId, visible }:
                 data-op-kind={op.kind}
                 data-op-error={op.isError ? 'true' : undefined}
                 data-selected={selectedCallId === op.callId ? 'true' : undefined}
-                onClick={() => { onPreview(path, op, knownContentBefore(ops, path, op)) }}
+                onClick={() => { onPreview(path, op) }}
               >
                 <span className={css.opKind} data-kind={op.kind}>
                   {t(op.kind === 'read' ? 'changesRead' : op.kind === 'write' ? 'changesWrite' : 'changesEdit')}
                 </span>
-                <span className={css.opTime}>{relativeTime(new Date(op.time).toISOString())}</span>
                 {op.running && <span className={css.opFlag}>{t('changesRunning')}</span>}
                 {op.isError && <span className={css.opFlagError}>{t('changesError')}</span>}
-                {op.kind !== 'read' && !op.isError && (
-                  <span className={css.opSize}>
-                    {formatBytes(new Blob([op.edit?.newString ?? op.content ?? '']).size)}
-                  </span>
-                )}
+                <span className={css.opMeta}>
+                  {op.kind !== 'read' && !op.isError && (
+                    <span className={css.opSize}>
+                      {formatBytes(new Blob([op.edit?.newString ?? op.content ?? '']).size)}
+                    </span>
+                  )}
+                  <span className={css.opTime}>{relativeTime(new Date(op.time).toISOString())}</span>
+                </span>
               </button>
             ))}
           </div>