fix(stop-metro): only kill the listener (keep execFileSync, no shell)

[latekvo]

Problem

stop-metro runs lsof -ti tcp:<port>, which returns every process with a socket on the port — including ESTABLISHED connections, not just the listener. The Argent tool-server holds a CDP client socket to Metro on that port, so stop-metro SIGTERMs the tool-server along with Metro (it then auto-respawns, dropping in-memory profiler session state and disrupting any connected editor).

Fix

Add -sTCP:LISTEN so only the process listening on the port (Metro) matches.

This keeps the existing execFileSync (no shell) call — port is never shell-interpreted, preserving the defense-in-depth in the original code.

Note: there is an existing branch fix/stop-metro-listener-only with the same -sTCP:LISTEN idea, but it switches to execSync with the port interpolated into a shell string. port is zod-validated to an int so it's safe in practice, but it reintroduces a shell surface the original deliberately avoided. This PR is the no-shell alternative — pick whichever you prefer.

Verification

Listener-vs-client repro: lsof -ti tcp:<port> returns both the listener and a connected client pid; lsof -ti tcp:<port> -sTCP:LISTEN returns only the listener.