fix: default to 0.0.0.0 to fix WSL2 health check failure (#520)

PR #470 changed the default listen host to undefined, letting Node.js
bind to IPv6 :: on systems that support it. This broke WSL2 where IPv6
dual-stack is unreliable — the server binds to :: but IPv4 127.0.0.1
connections fail, causing the health check to time out.

Revert to 0.0.0.0 as the default. Users who need IPv6 can set
BIND_HOST=:: explicitly.

Fixes #518

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

packages/server/src/services/hermes/gateway-manager.ts

@@ -120,6 +120,15 @@ interface ManagedGateway {
   process?: ChildProcess
 }
 
+function formatHostForUrl(host: string): string {
+  if (host.startsWith('[') && host.endsWith(']')) return host
+  return host.includes(':') ? `[${host}]` : host
+}
+
+function buildHttpUrl(host: string, port: number): string {
+  return `http://${formatHostForUrl(host)}:${port}`
+}
+
 // ============================
 // GatewayManager
 // ============================
@@ -360,7 +369,7 @@ export class GatewayManager {
     const gw = this.gateways.get(name)
     if (gw?.url) return gw.url
     const { port, host } = this.readProfilePort(name)
-    return `http://${host}:${port}`
+    return buildHttpUrl(host, port)
   }
 
   /** 读取 profile 的 API_SERVER_KEY（从 .env 文件） */
@@ -426,7 +435,7 @@ export class GatewayManager {
   async detectStatus(name: string): Promise<GatewayStatus> {
     const pid = this.readPidFile(name)
     const { port, host } = this.readProfilePort(name)
-    const url = `http://${host}:${port}`
+    const url = buildHttpUrl(host, port)
 
     if (pid && this.isProcessAlive(pid) && await this.checkHealth(url)) {
       this.gateways.set(name, { pid, port, host, url })
@@ -456,7 +465,7 @@ export class GatewayManager {
   async start(name: string): Promise<GatewayStatus> {
     const { port, host } = await this.resolvePort(name)
     const hermesHome = this.profileDir(name)
-    const url = `http://${host}:${port}`
+    const url = buildHttpUrl(host, port)
 
     if (needsRunMode) {
       // WSL / Docker：无 systemd/launchd，用 "gateway run" 作为 detached 子进程
@@ -534,7 +543,7 @@ export class GatewayManager {
     const gw = this.gateways.get(name)
     const url = gw?.url || (() => {
       const { port, host } = this.readProfilePort(name)
-      return `http://${host}:${port}`
+      return buildHttpUrl(host, port)
     })()
 
     if (!needsRunMode) {