Add bootstrap entry for env-based proxy support

Introduces bootstrap.js to set NODE_USE_ENV_PROXY before loading main.js, ensuring proxy support is enabled unless explicitly opted out. Updates action.yml to use bootstrap as the main entry and modifies build script to bundle bootstrap.js.

bootstrap.js

@@ -0,0 +1,7 @@
+// Enable env-based proxy support (honors explicit opt-out if caller set NODE_USE_ENV_PROXY)
+if (process.env.NODE_USE_ENV_PROXY == null) {
+  process.env.NODE_USE_ENV_PROXY = "1";
+}
+
+// Defer to original main entry (dynamic import ensures above code runs first)
+await import("./main.js");