Improvements

H2MUX Stability

• Added connection-level activity tracking that counts HTTP/2 control frames (PING, SETTINGS) as activity, ensuring keepalives properly reset idle detection
• Removed application-level idle timeout in favor of PING-based dead connection detection, matching sing-mux behavior for better compatibility
• Added drain timeout for graceful session shutdown
• Updated window sizes to match Go http2 defaults (256KB per stream, 1MB per connection)

AnyTLS Memory Leak Fixes

• Stream handler tasks are now tracked and aborted when session closes, preventing memory leaks from orphaned tasks
• Added 5-minute stream handler timeout to prevent hung streams (slow DNS, stuck connections) from leaking memory
• Reduced allocations in padding frame generation

TUN Connection Tracking

• Refactored TCP connection state machine with explicit states (Normal, Close, Closing, Closed) for proper lifecycle management
• Improved connection teardown handling following shadowsocks-rust patterns