refactor(server): replace Bun serve with Hono node adapters (#18335)

Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>
Co-authored-by: Luke Parker <10430890+Hona@users.noreply.github.com>
Co-authored-by: Adam <2363879+adamdotdevin@users.noreply.github.com>
Co-authored-by: Brendan Allan <git@brendonovich.dev>

packages/opencode/src/plugin/index.ts

@@ -130,7 +130,8 @@ export namespace Plugin {
             get serverUrl(): URL {
               return Server.url ?? new URL("http://localhost:4096")
             },
-            $: Bun.$,
+            // @ts-expect-error
+            $: typeof Bun === "undefined" ? undefined : Bun.$,
           }
 
           for (const plugin of INTERNAL_PLUGINS) {