## Why
Remote executions need managed-network proxy listeners in the executor so their
loopback proxy addresses are reachable by the launched process.
## What changed
- Add a capability-gated exec-server protocol field for executor-local proxy
launch configuration, including network policy, audit metadata, and execution
attribution.
- Start the proxy while preparing a remote process, replace inherited proxy
environment variables with its local addresses, and derive the sandbox
context from its listeners.
- Keep the proxy alive until inherited output streams close, then shut it down.
- Reject unsupported remote settings such as MITM and credential injection.
## Testing
- Cover configuration round trips and rejection of unsupported settings.
- Verify executor-local startup, blocked-domain enforcement, protocol
compatibility, and proxy lifetime through process closure.
GitOrigin-RevId: c984f54e3e600aa9ebcbf8cf4574046e2c199d11
9f6c29e281