refactor(sea): move default SOCKET_NODE_DOWNLOAD_URL to constants

Moved the default URL from inline fallback to the ENV constant definition
for better maintainability.

Changes:
- constants.mjs: Set default 'https://nodejs.org/download/release' in ENV
- build.mjs: Removed inline '|| default' fallback, use constant directly

Benefits:
- Single source of truth for default URL
- Cleaner code in downloadNodeBinary()
- Easier to update default URL in the future

Author: jdalton

packages/node-sea-builder/scripts/build.mjs

@@ -183,8 +183,7 @@ async function downloadNodeBinary(version, platform, arch) {
   // Alpine uses unofficial musl builds from unofficial-builds.nodejs.org.
   const baseUrl = isAlpine
     ? 'https://unofficial-builds.nodejs.org/download/release'
-    : constants.ENV.SOCKET_NODE_DOWNLOAD_URL ||
-      'https://nodejs.org/download/release'
+    : constants.ENV.SOCKET_NODE_DOWNLOAD_URL
 
   const archMap = {
     x64: 'x64',

packages/node-sea-builder/scripts/constants.mjs

@@ -11,7 +11,7 @@ const { versionSemver: NODE_VERSION } = nodeVersionConfig
 // Environment variables (can override defaults).
 const ENV = {
   SOCKET_CLI_SEA_NODE_VERSION: process.env.SOCKET_CLI_SEA_NODE_VERSION || NODE_VERSION,
-  SOCKET_NODE_DOWNLOAD_URL: process.env.SOCKET_NODE_DOWNLOAD_URL,
+  SOCKET_NODE_DOWNLOAD_URL: process.env.SOCKET_NODE_DOWNLOAD_URL || 'https://nodejs.org/download/release',
 }
 
 export default {