[FEATURE REQ] [Thin Client][Gateway V2] HTTP/2 channel health checker — PING-based liveness and broken connection eviction

[jeet1995]

Summary

HTTP/2 connections to the thin client proxy can become stale/broken without the SDK knowing. PING-based health checking detects and evicts dead channels; GOAWAY handling enables graceful rotation.

Acceptance Criteria

• PR created and merged
• PING frames detect dead HTTP/2 connections within health check interval
• Dead channels evicted from connection pool
• GOAWAY frames trigger graceful connection rotation
• Healthy connections preserved across health check cycles
• All 3 netem tests pass