Feature Request: Add cumulative cache token counts to status line input

Summary

The status line input JSON currently provides cumulative values for total_input_tokens and total_output_tokens, but only provides per-turn values for cache tokens via current_usage.cache_read_input_tokens and current_usage.cache_creation_input_tokens.

This inconsistency makes it impossible to display accurate cumulative cache usage in custom status lines.

Current Behavior

The status line input includes:

{
  "context_window": {
    "total_input_tokens": 21043,        // ✅ Cumulative
    "total_output_tokens": 11318,       // ✅ Cumulative
    "context_window_size": 200000,
    "used_percentage": 42,
    "remaining_percentage": 58,
    "current_usage": {
      "cache_read_input_tokens": 15000,      // ❌ Per-turn only
      "cache_creation_input_tokens": 5000    // ❌ Per-turn only
    }
  }
}

Meanwhile, Claude Code internally tracks cumulative cache values (visible in .claude.json):

• lastTotalCacheReadInputTokens
• lastTotalCacheCreationInputTokens

Requested Enhancement

Add cumulative cache token fields to the status line input:

{
  "context_window": {
    "total_input_tokens": 21043,
    "total_output_tokens": 11318,
    "total_cache_read_input_tokens": 1163037,      // 🆕 Cumulative
    "total_cache_creation_input_tokens": 202145,   // 🆕 Cumulative
    "context_window_size": 200000,
    "used_percentage": 42,
    "remaining_percentage": 58,
    "current_usage": {
      "cache_read_input_tokens": 15000,
      "cache_creation_input_tokens": 5000
    }
  }
}

Use Case

Custom status lines that want to display session-wide cache usage alongside input/output tokens. For example:

14:32 [Opus 4.5] myrepo • in:21k out:11k cache:1.3m (42%) [main +2]

Currently, the cache: value can only show the last turn's cache usage, which is inconsistent with how in: and out: display cumulative totals.

Environment

• Claude Code version: 2.1.29
• Platform: Linux (WSL2)

Additional Context

The data already exists internally (lastTotalCacheReadInputTokens, lastTotalCacheCreationInputTokens in project config), it just needs to be exposed in the status line input JSON.