🤖 Update bash sleep error to permit <10s sleeps in busy loops

[ammar-agent]

Observed many agents polling without sleep, draining resources. The error message now explicitly encourages the use of short sleeps in busy loops while discouraging standalone sleep commands.

Changes:

• Updated error message from "sleep commands are blocked" to "do not start commands with sleep; prefer <10s sleeps in busy loops"
• More permissive framing that validates sleep when used properly in polling loops
• Maintains blocking of standalone sleep commands at script start

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