Add refreshInterval option for statusLine command

Feature Request

Problem

The statusLine command script is only re-executed on specific events (assistant responses, permission mode changes, vim mode toggles). When Claude Code is idle, the status line becomes stale — any dynamic information (e.g., rate limit reset countdowns, elapsed time) quickly becomes inaccurate.

Proposed Solution

Add an optional refreshInterval property to the statusLine configuration:

{
  "statusLine": {
    "type": "command",
    "command": "bash \"$HOME/.claude/statusline.sh\"",
    "refreshInterval": 60
  }
}

• refreshInterval — interval in seconds to re-run the command script
• When omitted, behavior remains unchanged (event-driven only)
• The interval should be debounced/reset when an event-driven update already fires

Use Case

My status line script displays rate limit usage with countdown timers (resets_at timestamps formatted as relative time, e.g., 4h10m, 2d23h). These countdowns are only accurate at the moment the script runs. During idle periods, the displayed time drifts and becomes misleading.

A periodic refresh (even at a conservative interval like 60s) would keep dynamic status information reasonably accurate without significant overhead.

Alternatives Considered

• Embedding a background loop in the script itself — not viable since the script is invoked per-call and stdout is captured
• Accepting stale data — functional but degrades the UX of time-sensitive displays