[feature] For `codex-multi-auth-codex`, force specific account / pool

[tyteen4a03]

Problem Statement

I have different pools of personal and work Codex accounts. I would like be able to trigger Codex on my personal pool for a specific invocation of codex-multi-auth-codex (e.g. for use in T3 Code)

Proposed Solution

Allow --account to be specified when using codex-multi-auth-codex

Alternatives Considered

Scope

Validation Plan

Compliance Confirmation

• This proposal is for legitimate personal development workflows.
• This proposal does not request bypassing OpenAI controls or policies.
• This proposal does not introduce multi-tenant resale behavior.