support MCP elicitations (#6947)

No support for request schema yet, but we'll at least show the message
and allow accept/decline.

<img width="823" height="551" alt="Screenshot 2025-11-21 at 2 44 05 PM"
src="https://github.com/user-attachments/assets/6fbb892d-ca12-4765-921e-9ac4b217534d"
/>

codex-rs/protocol/src/approvals.rs

@@ -3,6 +3,7 @@ use std::path::PathBuf;
 
 use crate::parse_command::ParsedCommand;
 use crate::protocol::FileChange;
+use mcp_types::RequestId;
 use schemars::JsonSchema;
 use serde::Deserialize;
 use serde::Serialize;
@@ -53,6 +54,24 @@ pub struct ExecApprovalRequestEvent {
     pub parsed_cmd: Vec<ParsedCommand>,
 }
 
+#[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
+pub struct ElicitationRequestEvent {
+    pub server_name: String,
+    pub id: RequestId,
+    pub message: String,
+    // TODO: MCP servers can request we fill out a schema for the elicitation. We don't support
+    // this yet.
+    // pub requested_schema: ElicitRequestParamsRequestedSchema,
+}
+
+#[derive(Debug, Clone, Copy, Deserialize, Serialize, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "lowercase")]
+pub enum ElicitationAction {
+    Accept,
+    Decline,
+    Cancel,
+}
+
 #[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
 pub struct ApplyPatchApprovalRequestEvent {
     /// Responses API call id for the associated patch apply call, if available.