Follow-up to #94379 / #94394.

After #94394 landed the caller-scoped ensurePortAvailable(port, host?), the Chrome CDP caller was fixed, but startSshPortForward in src/infra/ssh-tunnel.ts still calls it host-less:

await ensurePortAvailable(localPort);

This re-introduces the exact #94379 flaw on the SSH-tunnel surface: on a dual-stack host the host-less probe binds the IPv6 wildcard :: and misses an IPv4-only occupant, so the preflight reports a busy port as free.

It's also internally inconsistent — every other probe in this module is pinned to IPv4 loopback:

• pickEphemeralPort → listen(0, "127.0.0.1")
• canConnectLocal → connect({ host: "127.0.0.1" })
• the forward itself → -L ${localPort}:127.0.0.1:${remotePort}

Fix: pass the interface this caller actually owns, matching #94394's pattern:

await ensurePortAvailable(localPort, "127.0.0.1");

Lower harm than the Chrome path (it only affects SSH-tunnel port selection, and it already falls back to an ephemeral port on EADDRINUSE), but it's the same root cause and a one-line scoped fix. Happy to send a PR.