Feature Request: Add plan/rate limit usage to status line JSON

Summary

Expose plan usage percentage (rate limit) in the status line JSON data, similar to how context_window.used_percentage is already exposed.

Motivation

When using a custom status line script, I want to display how much of my rate limit I've used before it resets. This information is already visible via /usage, but it's not available in the status line JSON.

This is arguably more important than context window usage because:

• Context window resets every conversation
• Rate limit affects your ability to work across all sessions
• Knowing you're at 80% rate limit helps you pace your work

Current behavior

The status line JSON includes:

{
  "context_window": {
    "used_percentage": 66,
    "remaining_percentage": 34,
    ...
  },
  "cost": {
    "total_cost_usd": 39.62,
    ...
  }
}

Requested behavior

Add a usage_limits or plan object:

{
  "usage_limits": {
    "used_percentage": 76,
    "remaining_percentage": 24,
    "resets_in_seconds": 6000,
    "resets_at": "2025-01-16T17:00:00Z"
  }
}

Use case

Custom status line showing plan usage with color coding (green/yellow/red) to help users monitor their rate limit at a glance, without needing to run /usage.

Environment

• Claude Code version: 2.1.9
• OS: macOS