Expose effort level in statusLine JSON data

Feature Request

The custom statusLine command receives JSON on stdin with fields like model, context_window, cost, rate_limits, etc. However, the current effort/reasoning level (set via /effort) is not included in this JSON.

Use case

I'd like to display the current effort level next to the model name in my custom status line, so I can see at a glance what reasoning effort is active (e.g. claude-opus-4-6 [high]).

Suggested change

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

{
  "effort": {
    "level": "high",
    "mode": "auto"
  }
}

Where level is the current effective level (low, medium, high) and mode indicates whether it was explicitly set or is auto.