Config tweaks for docker

- Remove `$` interpolation for env
- Allow puppeteer to work headless in docker, headful with npx

src/filesystem/README.md

@@ -109,6 +109,7 @@ Add this to your `claude_desktop_config.json`:
 Note: you can provide sandboxed directories to the server by mounting them to `/projects`. Adding the `ro` flag will make the directory readonly by the server.
 
 ### Docker
+Note: all directories must be mounted to `/projects` by default.
 
 ```json
 {
@@ -122,7 +123,6 @@ Note: you can provide sandboxed directories to the server by mounting them to `/
         "--mount", "type=bind,src=/Users/username/Desktop,dst=/projects/Desktop",
         "--mount", "type=bind,src=/path/to/other/allowed/dir,dst=/projects/other/allowed/dir,ro",
         "--mount", "type=bind,src=/path/to/file.txt,dst=/projects/path/to/file.txt",
-        "--env", "DOCKER_ROOT_WORKSPACE=/projects",
         "ai/mcp-filesystem"
       ]
     }