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/ServerRequest.json

@@ -41,7 +41,7 @@
     "ChatgptAuthTokensRefreshParams": {
       "properties": {
         "previousAccountId": {
-          "description": "Workspace/account identifier that Codex was previously using.\n\nClients that manage multiple accounts/workspaces can use this as a hint to refresh the token for the correct workspace.\n\nThis may be `null` when the prior ID token did not include a workspace identifier (`chatgpt_account_id`) or when the token could not be parsed.",
+          "description": "Workspace/account identifier that Codex was previously using.\n\nClients that manage multiple accounts/workspaces can use this as a hint to refresh the token for the correct workspace.\n\nThis may be `null` when the prior auth state did not include a workspace identifier (`chatgpt_account_id`).",
           "type": [
             "string",
             "null"