CLAUDE.md: use tofu -chdir instead of cd

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

CLAUDE.md

@@ -76,6 +76,16 @@ nix develop -c tofu plan
 tofu plan
 ```
 
+**OpenTofu:** Use the `-chdir` option instead of `cd` when running tofu commands in subdirectories:
+```bash
+# Good - uses -chdir option
+nix develop -c tofu -chdir=terraform plan
+nix develop -c tofu -chdir=terraform/vault apply
+
+# Avoid - changing directories
+cd terraform && tofu plan
+```
+
 ### Secrets Management
 
 Secrets are managed by OpenBao (Vault) using AppRole authentication. Most hosts use the