test(garden): deterministic setup for connection-refused activator test
Replace :gen_tcp.listen + close (whose socket-file lifecycle varies
across platforms) with a plain File.touch!. Connecting to a regular
file at {:local, path} reliably returns :econnrefused on Linux, which
is what the test needs to verify.
sow-167
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>