Add async iterator support for event subscriptions

[meshackyaro]

Description

Event API uses callbacks. Modern async code prefers async iterators for better integration.

Component

SDK

Difficulty

🟡 Medium

Tasks

• Add async iterator interface for events
• Support for-await-of pattern
• Maintain callback API for compatibility
• Add async iteration examples
• Test iterator cleanup

Acceptance Criteria

• Events consumable with for-await-of
• Both callback and iterator APIs work
• Examples demonstrate usage

Estimated Time

2-3 days