Expose plan usage quota and reset time in statusline JSON

Feature Request

Problem

The statusline JSON (stdin) provides context_window.used_percentage and cost fields, but does not include plan-level usage quota data that is already visible in the /usage UI:

• Session usage percentage (e.g., 4% used)
• Reset time (e.g., Resets 5:59pm Asia/Seoul)
• Weekly usage percentage (e.g., 25% used, all models)

Current Behavior

The /usage dialog shows this data, but there is no way to access it from a statusline script, CLI command, MCP server, or local file.

Proposed Solution

Add the following fields to the statusline JSON:

{
  "usage_quota": {
    "session": {
      "used_percentage": 4,
      "resets_at": "2026-03-18T17:59:00+09:00"
    },
    "weekly": {
      "used_percentage": 25,
      "resets_at": "2026-03-20T14:59:00+09:00"
    }
  }
}

Use Case

Displaying plan usage and reset time in the status line so users can monitor their quota without opening the /usage dialog.