[feature] Automatically try again on "selected model is at capacity"

[tyteen4a03]

Problem Statement

To work around issues where OpenAI sometimes report "selected model is at capacity", while the user needs to be away to initiate a long-running task.

Proposed Solution

Introduce an automatic retry mechanism for submitted messages.

Alternatives Considered

N/A

Scope

N/A

Validation Plan

When an OpenAI model is at capacity, codex-mulit-auth should continue to try again.

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.