chore: clean up home configuration and simplify arty.yml

- Add Rust cargo environment to .zshenv
- Make oh-my-zsh sourcing conditional in .zshrc for safer initialization
- Simplify arty.yml: remove env-specific repository references, clean formatting
- Remove unused .vscode/settings.json

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

.zshenv

@@ -1 +1,2 @@
 
+. "$HOME/.cargo/env"