Fixes#1126
Go type assertions return true for zero values, which caused recurring
cron jobs (every_seconds/cron_expr) to silently become one-time 'at' tasks
when LLMs filled unused optional parameters with default values (0).
Changes:
- Add validity checks after type assertions: atSeconds > 0, everySeconds > 0, cronExpr != ""
- This ensures zero values are treated as 'not set' rather than valid schedule values
- Recurring tasks like "remind me every 2 hours" now correctly create recurring jobs
Qiaochu Hu
7f6d95c026