fix(hosts): detach connection-close listener when host disconnects

[krazyjakee]

What

handleRegisterHost adds a listener to the process-global NorayEvents bus on every register-host command and never removes it. This makes the listener self-removing so it is detached once its socket has closed.

Fixes #81.

Why

In src/hosts/host.commands.ts, each register-host does:

NorayEvents.on("connection-close", (closed) => {
  if (closed !== socket) return;
  ...
});

NorayEvents (src/events.ts) is a module-level singleton whose EventBus stores handlers in a plain array that is only ever pushed to — there was no matching .off(...) anywhere. Since clients also issue register-host, every connection (host or client) permanently appends a closure that retains socket and host. Over time:

• Memory grows without bound (leaked closures + the sockets/hosts they capture).
• emit("connection-close", ...) becomes O(number of connections ever made), since each disconnect walks the entire accumulated array.
• Eventually the event loop is starved enough that the TCP socket still accepts connections while the command handler stops replying — the "port bound but process hung" symptom that requires a restart. This is the same class of unresponsiveness the dbg/unresponsive-tcp / fix/unresponsive-tcp branches appear to be investigating; those branches add diagnostics but don't detach this listener.

Reproduction

Against ghcr.io/foxssake/noray:main (v1.5.4), 15,000 connect → register-host → disconnect cycles:

	memory after 15k cycles	register-host reply latency
main	~29 → ~65 MiB (linear, retained)	drifting upward
this PR	~31 → ~43 → plateaus ~37 MiB (GC reclaims)	flat

Driver:

import socket
for _ in range(15000):
    s = socket.create_connection(("127.0.0.1", 8890), timeout=2)
    s.sendall(b"register-host\n")
    s.recv(256)
    s.close()

noray_active_hosts also stops drifting above the real host count with the fix.

Change

Extract the inline listener into a named onConnectionClose and call NorayEvents.off("connection-close", onConnectionClose) once it has handled its own socket's close. No behavioural change for a live host — only the cleanup that was missing.