xterm.js's onData hands the browser a plain string, and WebSocket.send(string)
always emits a TEXT frame — pty-attach.js only forwarded BINARY frames to
pty.write(), so every keystroke was silently dropped as an unparseable JSON
control message. Now any non-control text frame reaches the pty.
Deeper root cause of the terminal never accepting input at all: the /ws
WebSocketServer used the {server, path} shorthand, whose own internal
upgrade listener calls handleUpgrade() for every upgrade on the shared
http.Server and aborts with 400 on a path mismatch — killing /ws-pty/*
upgrades before the PTY server's own listener ever ran. Switched /ws to
noServer + a manual path-checked dispatch, matching /ws-pty's pattern.
nntrivi2001