docs: rewrite README to match current architecture

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -1,64 +1,52 @@
 # Fabric.Desktop
 
-Electron desktop shell for Fabric.Frontend.
+A **self-contained** Electron desktop app for Fabric. It bundles the
+`Fabric.Frontend` SPA inside the package and loads it locally over
+`file://` — no separate frontend web server is needed. It still talks to the
+Center/Guild **backends** over HTTP (the Center base is set on the login
+screen, so the desktop app points at whatever host runs the backends).
 
-## 功能（当前）
+## How it works
-- BrowserWindow 基础配置（尺寸/最小尺寸/标题）
-- Dev/Prod 加载策略（dev server / 本地 offline.html）
-- 基础菜单与快捷键（刷新、开发者工具、退出）
-- 安全基线：`contextIsolation` + `sandbox` + 禁止任意新窗口/导航
-- `preload + IPC` 白名单：
-  - `fabric:config:get`
-  - `fabric:config:set`
-  - `fabric:notify`
 
-## Dev
+- `npm run build:renderer` builds `Fabric.Frontend` with a relative asset
+  base (`build:desktop`) and copies the bundle into `renderer/`.
+- `main.js` loads `renderer/index.html` in production (falls back to
+  `offline.html` if the bundle is missing); dev mode loads
+  `FABRIC_DESKTOP_URL` (default `http://localhost:5173`).
+- Security baseline: `contextIsolation` + `sandbox`, no arbitrary new
+  windows/navigation; `preload` exposes a small IPC allowlist
+  (`fabric:config:get|set`, `fabric:notify`).
+- System tray (show/hide window, quit) with the Fabric tray icon; app/window
+  icons use the Fabric mark.
+
+## Develop
 
 ```bash
 npm install
-npm run start:dev
+npm run start:dev     # expects Fabric.Frontend dev server at :5173
+# or, against the bundled renderer:
+npm run build:renderer && npm start
 ```
 
-`start:dev` expects Frontend dev server at `http://localhost:5173`.
+## Build / package
-
-## Standalone
-
-```bash
-npm start
-```
-
-## Build / Release
-
-先安装依赖（包含 `electron-builder`）：
 
 ```bash
 npm install
+npm run pack          # unpacked dir (no installer)
+npm run dist:linux    # AppImage, deb, tar.gz   -> dist/
+npm run dist:mac      # dmg, zip
+npm run dist:win      # nsis, zip
 ```
 
-仅打包目录（不生成安装包）：
+Each `dist:*`/`pack` runs `build:renderer` first (so `Fabric.Frontend` must
+be present beside this submodule, which it is in the `Fabric` checkout).
+Output goes to `dist/` (git-ignored). `productName` is **Fabric** so the app
+installs to `/opt/Fabric/` (a space there breaks Electron's sandbox); the
+launcher is still labelled "Fabric Desktop". Linux icons are generated from
+`build/icons/`.
 
-```bash
+## Notes
-npm run pack
-```
 
-跨平台构建入口：
+- The bundled SPA uses `HashRouter` under `file://` (no server for the
-
+  History API). The Center/Guild backends are HTTP and CORS-allow the
-```bash
+  Electron `file://` origin (`null`).
-npm run dist
-```
-
-按平台构建：
-
-```bash
-npm run dist:linux
-npm run dist:mac
-npm run dist:win
-```
-
-构建产物输出到：
-
-- `dist/`
-
-产物命名规范：
-
-- `Fabric-Desktop-${version}-${os}-${arch}.${ext}`