fix(cdp): unblock HTTP control plane during synchronous V8 execution
Fixes#62.
Previously, the TCP accept loop and CDP processor shared a single-threaded
tokio LocalSet. Long synchronous JS evaluations starved the accept loop,
causing incoming connections to hang in the kernel backlog and effectively
killing the HTTP control plane.
This moves the TCP listener and `/json/*` endpoints to a dedicated OS
thread using `std::net::TcpListener`. HTTP requests are now handled
directly via blocking I/O on this thread, completely bypassing V8.
WebSocket connections are handed off to the LocalSet via a bounded mpsc
channel (capacity 128). If V8 stalls and the queue fills, new WS
connections are dropped (ECONNRESET) rather than buffering unboundedly
to prevent OOMs.
Includes a new integration test to verify the control plane stays
responsive during a 5s JS loop, plus inline documentation clarifying
thread lifetime semantics and a minor test TOCTOU race.
Sander Spilleman