[FEATURE] Allow specifying a specific model for a single turn

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

when i'm running claude i generally run sonnet for the speed of response, but i switch to opus for tasks i want to put more thought into. right now i can do this with /model but it's a persistent choice. it would be convenient if i could do this for a single turn, in the same way i can opt-into extended thinking via the think hard, think harder etc keywords.

https://docs.claude.com/en/docs/claude-code/common-workflows#use-extended-thinking

Proposed Solution

add a keyword to set the model

Alternative Solutions

currently i use /model but i often unintentionally leave my model in opus and burn through tokens i didn't intend to

Priority

Medium - Would be very helpful

Feature Category

Interactive mode (TUI)

Use Case Example

Example scenario:

1. i am interested in doing upfront planning as described in claude code's best practices to plan out a feature
2. i use a keyword like 'model:opus' in my prompt
3. after it's planned, i am back to my default model (sonnet) and proceed with implementation

Additional Context

_No response_