fix(app-server): for external auth, replace id_token with chatgpt_acc… (#11240)

…ount_id and chatgpt_plan_type

### Summary
Following up on external auth mode which was introduced here:
https://github.com/openai/codex/pull/10012

Turns out some clients have a differently shaped ID token and don't have
a chosen workspace (aka chatgpt_account_id) encoded in their ID token.
So, let's replace `id_token` param with `chatgpt_account_id` and
`chatgpt_plan_type` (optional) when initializing the external ChatGPT
auth mode (`account/login/start` with `chatgptAuthTokens`).

The client was able to test end-to-end with a Codex build from this
branch and verified it worked!

codex-rs/app-server-protocol/schema/json/ClientRequest.json

@@ -998,13 +998,20 @@
           "description": "[UNSTABLE] FOR OPENAI INTERNAL USE ONLY - DO NOT USE. The access token must contain the same scopes that Codex-managed ChatGPT auth tokens have.",
           "properties": {
             "accessToken": {
-              "description": "Access token (JWT) supplied by the client. This token is used for backend API requests.",
+              "description": "Access token (JWT) supplied by the client. This token is used for backend API requests and email extraction.",
               "type": "string"
             },
-            "idToken": {
-              "description": "ID token (JWT) supplied by the client.\n\nThis token is used for identity and account metadata (email, plan type, workspace id).",
+            "chatgptAccountId": {
+              "description": "Workspace/account identifier supplied by the client.",
               "type": "string"
             },
+            "chatgptPlanType": {
+              "description": "Optional plan type supplied by the client.\n\nWhen `null`, Codex attempts to derive the plan type from access-token claims. If unavailable, the plan defaults to `unknown`.",
+              "type": [
+                "string",
+                "null"
+              ]
+            },
             "type": {
               "enum": [
                 "chatgptAuthTokens"
@@ -1015,7 +1022,7 @@
           },
           "required": [
             "accessToken",
-            "idToken",
+            "chatgptAccountId",
             "type"
           ],
           "title": "ChatgptAuthTokensLoginAccountParams",