CLAUDE.md: prefer nix develop -c for devshell commands

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -61,10 +61,21 @@ Do not run `nix flake update`. Should only be done manually by user.
 ### Development Environment
 
 ```bash
-# Enter development shell (provides ansible, python3)
+# Enter development shell
 nix develop
 ```
 
+The devshell provides: `ansible`, `tofu` (OpenTofu), `vault` (OpenBao CLI), `create-host`, and `homelab-deploy`.
+
+**Important:** When suggesting commands that use devshell tools, always use `nix develop -c <command>` syntax rather than assuming the user is already in a devshell. For example:
+```bash
+# Good - works regardless of current shell
+nix develop -c tofu plan
+
+# Avoid - requires user to be in devshell
+tofu plan
+```
+
 ### Secrets Management
 
 Secrets are managed by OpenBao (Vault) using AppRole authentication. Most hosts use the