fix(core): swap bind-only 0.0.0.0 SSH gateway host for cluster URL host

CLI's resolve_ssh_gateway treated 0.0.0.0 as a loopback "keep as-is"
when the cluster URL was also loopback, so the SSH proxy connected to
0.0.0.0:port. The unspecified address is never a valid connect target
and is not present in any TLS cert SAN, which produced BadCertificate
TLS handshake failures during `openshell sandbox create -- ...` in
docker/podman e2e (e.g. bypass_detection).

Resolution: when the server returns 0.0.0.0 or :: as the gateway host
and both endpoints are loopback, fall back to the cluster URL's host
(which the CLI is already using to reach the gateway, so it must
resolve and match the cert).

Author: TaylorMutch

crates/openshell-core/src/forward.rs

@@ -462,7 +462,13 @@ pub fn resolve_ssh_gateway(
             // Remote cluster: use the remote host but keep the cluster URL port.
             return (host.to_string(), cluster_port);
         }
-        // Local cluster: both loopback — use cluster URL's port (Docker-mapped).
+        // Both endpoints loopback. The unspecified addresses (0.0.0.0 / ::)
+        // are bind-only — they aren't valid connect targets and aren't in TLS
+        // cert SANs, so fall back to the cluster URL's host (which the CLI
+        // is already using to reach the gateway).
+        if gateway_host == "0.0.0.0" || gateway_host == "::" {
+            return (host.to_string(), cluster_port);
+        }
         return (gateway_host.to_string(), cluster_port);
     }
 
@@ -693,6 +699,16 @@ mod tests {
         assert_eq!(port, 8080);
     }
 
+    #[test]
+    fn resolve_ssh_gateway_swaps_zeros_for_loopback_cluster_host() {
+        // The gateway binds 0.0.0.0 but advertises that bind address via the
+        // SSH session response. 0.0.0.0 is not a valid connect target and is
+        // not in any TLS cert SAN; fall through to the cluster URL's host.
+        let (host, port) = resolve_ssh_gateway("0.0.0.0", 8080, "https://127.0.0.1:9000");
+        assert_eq!(host, "127.0.0.1");
+        assert_eq!(port, 9000);
+    }
+
     #[test]
     fn resolve_ssh_gateway_handles_invalid_cluster_url() {
         let (host, port) = resolve_ssh_gateway("127.0.0.1", 8080, "not-a-url");