feat(core): Add Bun and Deno runtime support, unify core loader, unix-socket support and cross-runtime streaming/tests

ts/core_bun/index.ts

@@ -0,0 +1,3 @@
+// Core Bun exports - Bun's native fetch implementation with unix socket support
+export * from './response.js';
+export { CoreRequest } from './request.js';