Make Notification hook delay configurable

Feature Request

The Notification hook currently fires after a fixed ~30 second delay when Claude is waiting for user input. This delay is not configurable.

Use Case

When using a notification hook (e.g., macOS display notification with sound) to alert when Claude needs attention, the 30-second delay means the notification arrives noticeably late — by the time it fires, the user has already been waiting or has context-switched and lost more time than necessary.

Proposal

Allow configuring the notification delay in settings.json, e.g.:

{
  "hooks": {
    "Notification": [
      {
        "matcher": "",
        "timeout": 5,
        "hooks": [
          {
            "type": "command",
            "command": "osascript -e 'display notification \"Claude Code needs your attention\" with title \"Claude Code\" sound name \"Glass\"'"
          }
        ]
      }
    ]
  }
}

A timeout field (in seconds) on the Notification hook would let users tune the delay to their workflow. A shorter delay (e.g., 5-10s) would make the notification much more useful for users who want near-immediate alerts.

Current Workaround

None that preserves the "only notify when actually waiting for input" behavior. The Stop hook fires immediately but triggers on every response, including intermediate steps where Claude continues autonomously — making it too noisy.