fix wsl default listen host (#542)

tests/server/config.test.ts

@@ -2,8 +2,8 @@ import { describe, expect, it } from 'vitest'
 import { getListenHost } from '../../packages/server/src/config'
 
 describe('server config', () => {
-  it('does not force an IPv4 bind host by default', () => {
-    expect(getListenHost({})).toBeUndefined()
+  it('defaults to an IPv4 bind host', () => {
+    expect(getListenHost({})).toBe('0.0.0.0')
   })
 
   it('uses BIND_HOST when provided', () => {
@@ -11,6 +11,6 @@ describe('server config', () => {
   })
 
   it('ignores blank BIND_HOST values', () => {
-    expect(getListenHost({ BIND_HOST: ' ' })).toBeUndefined()
+    expect(getListenHost({ BIND_HOST: ' ' })).toBe('0.0.0.0')
   })
 })