Use shared npm/npm-next environments across both release workflows

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: smurching

.github/workflows/release-langchainjs.yml

@@ -20,7 +20,7 @@ jobs:
       id-token: write
       contents: write
     environment:
-      name: ${{ (github.event_name == 'push' || inputs.production) && 'npm-langchainjs' || 'npm-next-langchainjs' }}
+      name: ${{ (github.event_name == 'push' || inputs.production) && 'npm' || 'npm-next' }}
       url: https://www.npmjs.com/package/@databricks/langchainjs
     defaults:
       run: