Add extended thinking mode to statusline JSON input

Feature Request

The statusline command receives a JSON object via stdin with model info, context window stats, costs, etc. It would be useful to also include whether extended thinking mode is currently active.

Use Case

Custom statuslines can display the current model and version (e.g., "opus 4.6"), but there's no way to indicate whether extended thinking is enabled. This is useful context when working — thinking mode affects response quality, latency, and cost, so having it visible at a glance helps.

Proposed Addition

Add a field to the statusline JSON input, e.g.:

{
  "thinking": {
    "enabled": true,
    "budget_tokens": 10000
  }
}

Or at minimum:

{
  "thinking_enabled": true
}

Current Workaround

Reading ~/.claude/settings.json from the statusline script, but this is fragile and doesn't reflect runtime toggles.

Environment

• Claude Code CLI
• Custom statusline via settings.json → statusLine.command