Reapply "feat(core): optional mdns service (#6192)"

This reverts commit 505068d5a6.

packages/opencode/src/cli/cmd/serve.ts

@@ -1,29 +1,16 @@
+import { Config } from "../../config/config"
 import { Server } from "../../server/server"
 import { cmd } from "./cmd"
+import { withNetworkOptions, resolveNetworkOptions } from "../network"
 
 export const ServeCommand = cmd({
   command: "serve",
-  builder: (yargs) =>
-    yargs
-      .option("port", {
-        alias: ["p"],
-        type: "number",
-        describe: "port to listen on",
-        default: 0,
-      })
-      .option("hostname", {
-        type: "string",
-        describe: "hostname to listen on",
-        default: "127.0.0.1",
-      }),
+  builder: (yargs) => withNetworkOptions(yargs),
   describe: "starts a headless opencode server",
   handler: async (args) => {
-    const hostname = args.hostname
-    const port = args.port
-    const server = Server.listen({
-      port,
-      hostname,
-    })
+    const config = await Config.get()
+    const opts = resolveNetworkOptions(args, config)
+    const server = Server.listen(opts)
     console.log(`opencode server listening on http://${server.hostname}:${server.port}`)
     await new Promise(() => {})
     await server.stop()