fix: ensure every variant of ClientRequest has a params field (#4512)

This ensures changes the generated TypeScript type for `ClientRequest`
so that instead of this:

```typescript
/**
 * Request from the client to the server.
 */
export type ClientRequest =
  | { method: "initialize"; id: RequestId; params: InitializeParams }
  | { method: "newConversation"; id: RequestId; params: NewConversationParams }
  // ...
  | { method: "getUserAgent"; id: RequestId }
  | { method: "userInfo"; id: RequestId }
  // ...
```

we have this:

```typescript
/**
 * Request from the client to the server.
 */
export type ClientRequest =
  | { method: "initialize"; id: RequestId; params: InitializeParams }
  | { method: "newConversation"; id: RequestId; params: NewConversationParams }
  // ...
  | { method: "getUserAgent"; id: RequestId; params: undefined }
  | { method: "userInfo"; id: RequestId; params: undefined }
  // ...
```

which makes TypeScript happier when it comes to destructuring instances
of `ClientRequest` because it does not complain about `params` not being
guaranteed to exist anymore.

codex-rs/protocol/src/mcp_protocol.rs

@@ -158,6 +158,10 @@ pub enum ClientRequest {
     LoginChatGpt {
         #[serde(rename = "id")]
         request_id: RequestId,
+
+        #[ts(type = "undefined")]
+        #[serde(skip_serializing_if = "Option::is_none")]
+        params: Option<()>,
     },
     CancelLoginChatGpt {
         #[serde(rename = "id")]
@@ -167,6 +171,10 @@ pub enum ClientRequest {
     LogoutChatGpt {
         #[serde(rename = "id")]
         request_id: RequestId,
+
+        #[ts(type = "undefined")]
+        #[serde(skip_serializing_if = "Option::is_none")]
+        params: Option<()>,
     },
     GetAuthStatus {
         #[serde(rename = "id")]
@@ -176,6 +184,10 @@ pub enum ClientRequest {
     GetUserSavedConfig {
         #[serde(rename = "id")]
         request_id: RequestId,
+
+        #[ts(type = "undefined")]
+        #[serde(skip_serializing_if = "Option::is_none")]
+        params: Option<()>,
     },
     SetDefaultModel {
         #[serde(rename = "id")]
@@ -185,10 +197,18 @@ pub enum ClientRequest {
     GetUserAgent {
         #[serde(rename = "id")]
         request_id: RequestId,
+
+        #[ts(type = "undefined")]
+        #[serde(skip_serializing_if = "Option::is_none")]
+        params: Option<()>,
     },
     UserInfo {
         #[serde(rename = "id")]
         request_id: RequestId,
+
+        #[ts(type = "undefined")]
+        #[serde(skip_serializing_if = "Option::is_none")]
+        params: Option<()>,
     },
     FuzzyFileSearch {
         #[serde(rename = "id")]