fix(arty): source nvm.sh before nvm install

nvm is a shell function, not a binary — it doesn't survive into arty's
subprocess. Sourcing nvm.sh inline makes it available.

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

arty.yml

@@ -56,7 +56,7 @@ scripts:
   rust:install: curl https://sh.rustup.rs -sSf | sh -s -- --no-modify-path -y
   rust:install:tools: cargo install bat fd-find yazi-build
   rust:update: rustup update
-  node:install: nvm install
+  node:install: . "$HOME/.nvm/nvm.sh" && nvm install
   node:install:base: npm i -g npm pnpm
   ruby:install: rbenv install
   ruby:install:base: gem install bundler