feat: add CacheTimer widget for prompt cache TTL countdown

[tuansondinh]

Summary

Adds a new cache-timer widget that displays the remaining time on Anthropic's 5-minute prompt cache TTL directly in the status line.

No external dependencies. The widget reads the last assistant message timestamp directly from the transcript_path that Claude Code already passes to ccstatusline — no hooks, no additional tools required.

How it works

On each status line refresh, the widget:

1. Reads the last few bytes of the transcript JSONL file
2. Finds the most recent type: "assistant" entry
3. Computes remaining = 300s − elapsed from that timestamp

Display states:

Output	Meaning
🟢 4:52	Cache warm, >50% remaining
🟡 1:30	Draining, 20–50% remaining
🔴 0:15	Almost cold, <20% remaining
❄️ COLD	Cache expired

Usage

Add cache-timer to your layout via the TUI or directly in ~/.config/ccstatusline/settings.json:

{ "type": "cache-timer" }

Pair with refreshInterval: 1 in your Claude Code statusLine config so the countdown ticks in real time when the agent is idle:

"statusLine": {
  "type": "command",
  "command": "npx -y ccstatusline@latest",
  "refreshInterval": 1
}

Files changed

• src/widgets/CacheTimer.ts — new widget
• src/widgets/index.ts — export
• src/utils/widget-manifest.ts — registration