## Why
Windows firewall enforcement is tied to the logon-user sandbox identities. Proxy-enforced commands therefore need the elevated backend even when the configured sandbox mode is the default restricted-token mode.
## What changed
- Select the elevated Windows sandbox backend whenever a command uses the managed network proxy.
- Remove configuration and startup checks that required users or managed requirements to select the elevated sandbox explicitly.
- Start and expose managed network proxy state consistently on Windows.
## Testing
- Verify that proxy enforcement selects the elevated backend for the restricted-token sandbox mode.
GitOrigin-RevId: e01ac052587721c468a8fbcf4e2c7c5a185a3e05