Feature Request: Expose extended thinking mode status in statusline JSON API

Feature Request

Summary

Add extended thinking mode information to the JSON data piped to the statusline script.

Current State

The statusline JSON API currently provides model info, costs, and context usage, but has no thinking-related fields.

Use Case

Users want visibility into extended thinking activity in their statusline, similar to how we can display:

• Model name and context size
• Session costs
• Context window usage

Knowing when extended thinking is active helps users:

• Understand response behavior and timing
• Track token usage patterns
• Verify that extended thinking is enabled and working
• Monitor the value provided by extended thinking

Requested Fields

Add a thinking object to the statusline JSON API:

{
  "thinking": {
    "enabled": true,
    "active": false,
    "session_tokens": 15234
  },
  "context_window": {
    "total_thinking_tokens": 15234
  }
}

Fields:

• thinking.enabled - Whether extended thinking is enabled in settings
• thinking.active - Whether thinking has occurred in recent messages
• thinking.session_tokens - Total thinking tokens used this session
• context_window.total_thinking_tokens - Include thinking in token totals

Benefits

• Real-time thinking status for statusline display
• Consistent with existing metrics (cost, context, model)
• Better transparency for extended thinking mode
• Helps users understand token usage and costs

This would make extended thinking mode more observable and help users understand how their sessions are utilizing this feature.