test: lock in HOST validation and bind-interface control (E00-S04-T04)

Extend the env-adapter suite to the issue's reworked acceptance criteria:
- static assertions: the adapter resolves HOST via resolveHost (hostname/IP at
  the adapter boundary) and the server passes config.host to server.listen
- deterministic boundary probe: valid HOST forms (IPv4/IPv6/hostname) pass,
  invalid HOST forms throw ConfigStartupError naming host
- boot probes: HOST=127.0.0.1 binds loopback only (no answer on a
  non-loopback interface) with the startup log reflecting the actual bind;
  an invalid HOST exits non-zero naming the field without echoing the raw
  value
- mutation probes: bypassing resolveHost or dropping config.host from
  server.listen both fail
- config-startup-error: update the order-asserion mutation probe for the new
  server.listen(config.port, config.host, ...) signature

tests/config-startup-error.test.mjs

@@ -291,8 +291,8 @@ test('moving the adapter call after the server binds fails the order assertion (
   const moved = src
     .replace('const config = loadConfigFromEnv();\n', '')
     .replace(
-      'server.listen(config.port, () => {',
-      'server.listen(config.port, () => {\n  const config = loadConfigFromEnv();',
+      'server.listen(config.port, config.host, () => {',
+      'server.listen(config.port, config.host, () => {\n  const config = loadConfigFromEnv();',
     );
   assert.notEqual(moved, src, 'the mutation must actually move the adapter call after the bind');
   assert.throws(() => assertServerStartupValidation(moved), /before the server binds/);