docs(cron): show how to view scheduled tasks

[yzxlr]

📝 Description

Answer issue #1501 directly in both the README and CLI help.

Changes:

• Add an explicit picoclaw cron list example to the README section about scheduled tasks
• Document the related disable, enable, and remove commands in the same section
• Add help text/examples to the picoclaw cron root command and picoclaw cron list
• Extend cron command tests to cover the new help text

🔗 Related Issue

Fixes #1501

🧪 Verification

• go test ./cmd/picoclaw/internal/cron

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[afjcjsbx]

LGTM

[afjcjsbx]

pls, could you fix conflicts? 🙏