Add WebSocket and Server-Sent Events (SSE) support

[lonexreb]

Summary

Extend discovery pipeline to capture and represent WebSocket and SSE streaming APIs.

Problem

Currently only HTTP request/response traffic is captured. Modern apps heavily use WebSocket (chat, real-time data) and SSE (notifications, live feeds). These appear in CDP but are filtered out.

Implementation

• Capture WebSocket frames during CDP interception
• Detect SSE endpoints (Content-Type: text/event-stream)
• Model streaming APIs in OpenAPI spec extensions
• Generate clients with async streaming support

Files

• src/site2cli/discovery/capture.py — CDP WebSocket frame capture
• src/site2cli/discovery/analyzer.py — streaming pattern detection