Stream device screen for real-time preview

[obj-p]

Add a streaming mode for preview rendering that continuously sends screen updates rather than requiring explicit preview_snapshot calls.

Potential approaches

iOS Simulator:

• Facebook's IDB (idb_companion) supports video streaming from simulators — could be used directly or as reference for the protocol
• SimDeviceFramebufferService (IOSurface) for direct framebuffer access (related to Direct framebuffer screenshot via IOSurface #11)
• simctl io recordVideo as a fallback

macOS:

• CGWindowListCreateImage polling
• NSView.cacheDisplay for content-only frames (related to Content-only snapshots without window chrome #15)

Transport:

• Server-sent events or streaming MCP response with periodic frame data
• WebSocket-based frame streaming

This would enable AI agents to observe animations, transitions, and real-time state changes without polling snapshot calls.