## What changed
- Add `RemoteEnvironmentOptions` and `upsert_environment_with_options` so embedding hosts can attach trusted HTTP headers to remote exec-server WebSocket handshakes.
- Preserve the headers across session reconnects while redacting them from debug output.
- Reject invalid, duplicate, and WebSocket-controlled headers, and require `wss://` for non-loopback destinations.
- Connect header-bearing loopback WebSockets directly, with DNS results restricted to loopback addresses.
## Testing
- Cover header validation and redaction, delivery on initial connections and reconnects, and loopback destination enforcement.
GitOrigin-RevId: f2e2b0456c8e33c13fd8ab4ee040a8b5c15e885d
## What changed
- Add `EnvironmentManager::from_accepted_websocket` so embedding hosts can
construct a remote environment from an already accepted and authenticated
Axum WebSocket.
- Add `replace_accepted_websocket` to retire the current transport and resume
the same exec-server session on a host-supplied replacement connection.
- Serialize replacement handoffs, reject overlapping replacements, and release
the handoff claim when a replacement attempt is cancelled or fails.
## Testing
- Cover initial connection validation and immediate environment readiness.
- Verify replacement retry behavior and recovery of a running process and its
output after reconnecting.
GitOrigin-RevId: 1f2ab7bcf7b5abbbece5c101801432dc84a8058d
