[wieslawsoltes]

Independent WebSocket connections shared one global receive FIFO, allowing a bulk connection to delay a latency-sensitive protocol byte on another connection. Keep FIFO ordering within each socket and round-robin sockets with pending events while preserving the existing global count/byte limits and empty-to-ready wake behavior.

This advances #289 and #280. It closes the cross-socket starvation mode; #289 remains open for the separately measured cold extension-host process launch.

Validation:

• native two-socket gate: a one-byte marker is event 2 while a peer queues 128 × 4 KiB frames
• browser WebSocket lifecycle: 100/100 cycles, p95 0.192 ms
• product-shaped protocol lifecycle: 20/20 cycles, Ready p95 2.65 ms, Initialized p95 11.91 ms
• FileReader/timer regression: pass, 64-timer backlog in 0.324 ms
• exact clean SDK: 2,906 files, manifest verified, compiler/runtime profile verified
• AppScene host suite: 31/31 pass
• unchanged Code OSS exact workspace function: selected root/provider/5 resolved/5 model/5 visible/64 DOM nodes pass; resolve 1,300 ms
• product first paint remains red at 2,375 ms; retained server evidence attributes the remaining 908 ms transport→Ready interval to cold Node extension-host process launch, while Node Ready→WebScene dispatch is 44 ms

Evidence: docs/validation/websocket-per-socket-fairness-20260921.md; local product log /private/tmp/vscode-demo-workspace-ae37b204-run2.log.