fix(config): guard nvm use within the nvm.sh existence check

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

Author: nanotaboada

.envrc

@@ -1,3 +1,2 @@
 export NVM_DIR="$HOME/.nvm"
-[ -s "$NVM_DIR/nvm.sh" ] && source "$NVM_DIR/nvm.sh"
-nvm use
+[ -s "$NVM_DIR/nvm.sh" ] && source "$NVM_DIR/nvm.sh" && nvm use