Add notification behavior doc and suppress step alert in foreground

[jjoonleo]

Summary

• add documenting push/local notification business behavior and routing
• suppress case-3 (step transition) local notification display while app is foreground ()

Changes

• • guard in to early-return when lifecycle state is
• • runtime/business behavior reference for notification flows across Android/iOS/Web

Notes

• push notification handling remains unchanged
• step-transition notifications are only suppressed during foreground use

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[github-actions]

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