[FEATURE] Option to make Plan mode always use Opus 4.6 even if model is set to Sonnet 4.6

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

In plan mode, I want to use the highest ranking and rated model, currently Opus 4.6 to leverage its strenghts, and then Sonnet 4.6 to be the work horse to implement

Proposed Solution

In plan mode, I want to use the highest ranking and rated model, currently Opus 4.6 to leverage its strenghts, and then Sonnet 4.6 to be the work horse to implement

Alternative Solutions

_No response_

Priority

High - Significant impact on productivity

Feature Category

Performance and speed

Use Case Example

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Additional Context

_No response_