Expose /context per-category breakdown to status line scripts

Problem

The /context slash command shows a useful breakdown of context-window usage by category — System prompt, System tools, MCP tools, Memory files, Skills, Messages, Free space. This data is computed internally and rendered in the TUI only.

Status line scripts receive a JSON payload on stdin with context_window.current_usage.{input,cache_creation,cache_read,output}_tokens — aggregate counts only. There's no way to surface the per-category breakdown in a custom status line, even though Claude Code already computes it.

Request

Add the /context per-category breakdown to the status line JSON payload, e.g.:

"context_window": {
  ...
  "category_breakdown": {
    "system_prompt": 4100,
    "system_tools": 12700,
    "mcp_tools": 1900,
    "memory_files": 10500,
    "skills": 1200,
    "messages": 9400,
    "free_space": 962200
  }
}

Why

Power users who pay attention to context economy want this visible at all times, not on-demand via /context. Today the only signal in the status line is total tokens and the cost-tiered input/cache/output split, which doesn't tell you what is consuming the window.

Alternative

A claude context --json CLI subcommand would also work — status line scripts could shell out to it.

Version

Claude Code 2.1.138