feat: add self-contained offline development resources

README.md

@@ -2,6 +2,8 @@
 
 FreeCAD-aligned web CAD frontend baseline for the BitBybit runtime boundary.
 
+本机断网开发、资源同步、校验和恢复入口见 [离线资源库说明](docs/offline-development.zh-CN.md)。
+
 ## Current scope
 
 - React + Vite frontend shell
@@ -25,7 +27,7 @@ The current milestone is a facade-first integration slice. Part Design document
 ./npmw run dev
 ```
 
-The repository uses a project-local, checksum-verified Node.js `22.23.2` runtime and npm `10.9.8`. The wrapper downloads it to the ignored `.runtime/` directory and never changes `/usr/bin/node`; this removes the engine warning caused by running npm with an older system Node. `./nodew` runs the same pinned Node directly. See [docs/project-runtime.zh-CN.md](docs/project-runtime.zh-CN.md) for recovery and CI rules.
+The repository uses a project-local, checksum-verified Node.js `22.23.2` runtime and npm `10.9.8`. The wrapper restores it from the local resource library first, or downloads it when online, into the ignored `.runtime/` directory and never changes `/usr/bin/node`; this removes the engine warning caused by running npm with an older system Node. `./nodew` runs the same pinned Node directly. See [docs/project-runtime.zh-CN.md](docs/project-runtime.zh-CN.md) for recovery and CI rules.
 
 Build verification: