feat(design): integrate agent activity timeline

.project-docs/20-architecture/data-flow.md

@@ -30,6 +30,7 @@
 | 客户端更新检查 | 设置页 | Renderer update store → IPC → Main AppUpdater → 目标 feed | Main 记录并重抛原始错误；Renderer 只显示去重、脱敏的单条提示，稳定源缺包不伪装为最新版 |
 | Design Workspace load | Canvas/Sidebar | Renderer Host API → Main-owned Works Square V2 adapter → current Workspace/Direction/Living Form projection | 一个 Workspace 公开一个 current Direction 与 persistent Agent Session；conversation timeline 是交互历史，不是独立 authority object |
 | Design input and reconciliation | Chat/direct edit/decision/proposal/lock/Asset binding/restore | Renderer draft → Main → `design.input.apply` → canonical Direction projection | 全部进入同一 reducer；accepted 前 draft 保持本地，revision conflict 刷新权威投影，unknown result 复用原 command/operation identity |
+| Design activity and reply streaming | Direction Gateway journal | Main 固定活动阶段归一化 → Renderer operation-scoped activity；committed assistant delta → matching provisional assistant bubble → canonical Turn | `design.assistant.progress` 只显示在对应 optimistic user message 下方，不成为消息或右侧摘要；`design.assistant.delta` 只投影已提交回复。两者都按 Workspace、Direction、operation identity 和 replay cursor 收敛，均不改写 Specification |
 | 设计有限请求生命周期 | Renderer Workspace JSON 调用 / shared Works token refresh | Main deadline → Electron transport → safe-read-only Node fallback → Host API timeout envelope | 包括取凭据、请求头和响应 body 的完整生命周期最多 30 秒；超时 abort transport 并稳定返回 `504 DESIGN_WORKSPACE_REQUEST_TIMEOUT`；透明 fallback 只允许 `GET`/`HEAD`/`OPTIONS`，mutation 不隐式重放 |
 | Design Asset binding | 当前 Workspace 已完成图片 / 本地上传 | canonical Asset → typed `asset_binding` input → Current Specification revision | 图片/视频用途由 Specification medium 和 binding role 决定；只提交真实 Workspace Asset identity，不使用本地路径或自然语言占位 |
 | Design Quote and confirmation | 当前 exact Specification revision | `design.quote.request` → immutable public Quote projection → `design.generation.confirm` with Quote ID | Renderer 只展示 output summary、warnings、expiry、Token Points；Provider Prompt/model/route/storage/internal billing 不下发或编辑 |
@@ -81,4 +82,4 @@
 
 ## Last Updated
 
-2026-09-06
+2026-09-07