Feature request: Add reasoning effort level to statusline JSON input

Feature Request

Summary

Add the current reasoning effort level (e.g., low, medium, high) to the JSON data passed to the statusline command script.

Motivation

The statusline is a great way to display session context at a glance. Currently, model.id, model.display_name, context_window, cost, and output_style are available — but the reasoning effort level is missing.

When toggling between effort levels (e.g., via /fast), there's no persistent visual indicator of the current setting. Displaying it in the statusline would help users stay aware of their current configuration.

Proposed Solution

Add an effort or reasoning_effort field to the statusline JSON input, e.g.:

{
  "model": {
    "id": "claude-opus-4-6",
    "display_name": "Opus",
    "effort": "high"
  }
}

Or as a top-level field:

{
  "reasoning_effort": "high"
}

Use Case

Users who customize their statusline scripts can then display the effort level alongside model info, e.g.:

🧠 ████░░░░░░░░░░░░ 25% │ 💪 claude-opus-4-6 (high) │ 💰 $0.05

Thank you!