[FEATURE] Opusplan model with 1M tokens

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

I like to use opusplan model. since there exists opus[1m] and sonnet[1m], i wish to be able to use the same in opusplan eg opusplan[1m].

Proposed Solution

add possibility to use 1M tokens in opusplan mode

Alternative Solutions

_No response_

Priority

High - Significant impact on productivity

Feature Category

Configuration and settings

Use Case Example

_No response_

Additional Context

_No response_