CronCreate durable flag doesn't persist to scheduled_tasks.json

Bug

CronCreate with durable: true does not persist the scheduled task. The tool schema documents a durable parameter:

true = persist to .claude/scheduled_tasks.json and survive restarts

But when called with durable: true:

1. The output still says "Session-only (not written to disk, dies when Claude exits)"
2. ~/.claude/scheduled_tasks.json is never created
3. The task does not survive session restarts

Reproduction

1. Call CronCreate with durable: true:

{
  "cron": "*/5 * * * *",
  "prompt": "any prompt",
  "recurring": true,
  "durable": true
}

1. Check output — says "Session-only"
2. Check ~/.claude/scheduled_tasks.json — file does not exist

Expected

• Output should confirm the task is durable
• ~/.claude/scheduled_tasks.json should be created with the task
• Task should fire in subsequent sessions

Environment

• Claude Code CLI
• Linux (Ubuntu-based)
• Claude Opus 4.6 (1M context)