Update Codex login success page UX (#20136)

## Summary

update the local login success page to match the Codex desktop auth UX
use theme-aware colors and an inline 20px Codex mark
keep the actual localhost success page aligned with the browser auth UX
PR

## Tests

<img width="1728" height="1117" alt="Screenshot 2026-04-29 at 12 00
34 PM"
src="https://github.com/user-attachments/assets/76a40c3f-07c3-452c-97da-e7c43717cd2c"
/>

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -2227,7 +2227,9 @@ mod tests {
     fn serialize_account_login_chatgpt() -> Result<()> {
         let request = ClientRequest::LoginAccount {
             request_id: RequestId::Integer(3),
-            params: v2::LoginAccountParams::Chatgpt,
+            params: v2::LoginAccountParams::Chatgpt {
+                codex_streamlined_login: false,
+            },
         };
         assert_eq!(
             json!({
@@ -2242,6 +2244,28 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn serialize_account_login_chatgpt_streamlined() -> Result<()> {
+        let request = ClientRequest::LoginAccount {
+            request_id: RequestId::Integer(3),
+            params: v2::LoginAccountParams::Chatgpt {
+                codex_streamlined_login: true,
+            },
+        };
+        assert_eq!(
+            json!({
+                "method": "account/login/start",
+                "id": 3,
+                "params": {
+                    "type": "chatgpt",
+                    "codexStreamlinedLogin": true
+                }
+            }),
+            serde_json::to_value(&request)?,
+        );
+        Ok(())
+    }
+
     #[test]
     fn serialize_account_login_chatgpt_device_code() -> Result<()> {
         let request = ClientRequest::LoginAccount {

codex-rs/app-server-protocol/src/protocol/v2.rs

@@ -2174,9 +2174,12 @@ pub enum LoginAccountParams {
         #[ts(rename = "apiKey")]
         api_key: String,
     },
-    #[serde(rename = "chatgpt")]
-    #[ts(rename = "chatgpt")]
-    Chatgpt,
+    #[serde(rename = "chatgpt", rename_all = "camelCase")]
+    #[ts(rename = "chatgpt", rename_all = "camelCase")]
+    Chatgpt {
+        #[serde(default, skip_serializing_if = "std::ops::Not::not")]
+        codex_streamlined_login: bool,
+    },
     #[serde(rename = "chatgptDeviceCode")]
     #[ts(rename = "chatgptDeviceCode")]
     ChatgptDeviceCode,