Remove WebSocket transport from code-mode hosts (#40692)

## What changed

- Accept only `http://` and `https://` gRPC endpoints for app server
  `--code-mode-host` connections.
- Limit the standalone code-mode host to stdio and gRPC listeners.
- Remove the WebSocket session provider, dual-WebSocket negotiation, transport
  lanes, and related dependencies and tests.
- Keep coverage for shared and prewarmed gRPC hosts and reject WebSocket host
  URLs in CLI parsing tests.

GitOrigin-RevId: 8792604e79ffd54ce776074a4dc3f7d55e63752a

codex-rs/code-mode-protocol/src/host/message.rs

@@ -12,7 +12,6 @@ use super::ProtocolVersion;
 use super::RequestId;
 use super::SessionId;
 use super::SupportedProtocolVersions;
-use super::TransportLane;
 use super::WireCellId;
 use super::WireExecuteRequest;
 use super::WireNestedToolCall;
@@ -107,8 +106,6 @@ impl std::error::Error for ClientHelloError {}
 pub struct HostHello {
     selected_version: ProtocolVersion,
     capabilities: CapabilitySet,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    bulk_connection_token: Option<String>,
 }
 
 impl HostHello {
@@ -116,15 +113,9 @@ impl HostHello {
         Self {
             selected_version,
             capabilities,
-            bulk_connection_token: None,
         }
     }
 
-    pub fn with_bulk_connection_token(mut self, token: String) -> Self {
-        self.bulk_connection_token = Some(token);
-        self
-    }
-
     pub fn selected_version(&self) -> ProtocolVersion {
         self.selected_version
     }
@@ -132,10 +123,6 @@ impl HostHello {
     pub fn capabilities(&self) -> &CapabilitySet {
         &self.capabilities
     }
-
-    pub fn bulk_connection_token(&self) -> Option<&str> {
-        self.bulk_connection_token.as_deref()
-    }
 }
 
 /// Messages sent from a client to the code-mode host.
@@ -155,30 +142,6 @@ pub enum ClientToHost {
     },
 }
 
-impl ClientToHost {
-    /// Keeps notification acknowledgments with control traffic and tool results on the bulk lane.
-    pub fn transport_lane(&self) -> TransportLane {
-        match self {
-            Self::DelegateResponse {
-                result:
-                    WireResult::Ok {
-                        value: DelegateResponse::NotificationDelivered,
-                    },
-                ..
-            }
-            | Self::ClientHello(_)
-            | Self::Request { .. }
-            | Self::CancelRequest { .. } => TransportLane::Control,
-            Self::DelegateResponse { .. } => TransportLane::Bulk,
-        }
-    }
-
-    /// Validates the message families accepted by each paired socket.
-    pub fn allows_transport_lane(&self, lane: TransportLane) -> bool {
-        self.transport_lane() == lane
-    }
-}
-
 /// Messages sent from the code-mode host to a client.
 #[derive(Debug, Deserialize, PartialEq, Serialize)]
 #[serde(deny_unknown_fields, tag = "type", rename_all_fields = "camelCase")]
@@ -212,33 +175,6 @@ pub enum HostToClient {
     },
 }
 
-impl HostToClient {
-    /// Keeps notifications with control traffic and nested-tool callbacks on the bulk lane.
-    pub fn transport_lane(&self) -> TransportLane {
-        match self {
-            Self::DelegateRequest {
-                request: DelegateRequest::InvokeTool { .. },
-                ..
-            }
-            | Self::CancelDelegateRequest { .. } => TransportLane::Bulk,
-            Self::DelegateRequest {
-                request: DelegateRequest::Notify { .. },
-                ..
-            }
-            | Self::HostHello(_)
-            | Self::HandshakeRejected { .. }
-            | Self::Response { .. }
-            | Self::InitialResponse { .. }
-            | Self::CellClosed { .. } => TransportLane::Control,
-        }
-    }
-
-    /// Rejects messages received on the wrong paired socket.
-    pub fn allows_transport_lane(&self, lane: TransportLane) -> bool {
-        self.transport_lane() == lane
-    }
-}
-
 #[derive(Clone, Debug, Deserialize, PartialEq, Serialize)]
 #[serde(deny_unknown_fields, tag = "method", rename_all_fields = "camelCase")]
 pub enum HostRequest {