fix(terraform): add command guard and document missing aliases

- Add command existence check at the top of the plugin to prevent
  aliases and functions from being created when terraform is not
  installed, consistent with other plugins (e.g. bun, volta, gh)
- Add missing `tfapp` and `tfpo` aliases to the README documentation

plugins/terraform/README.md

@@ -21,6 +21,7 @@ plugins=(... terraform)
 | `tfa`   | `terraform apply`                      |
 | `tfa!`  | `terraform apply -auto-approve`        |
 | `tfap`  | `terraform apply -parallelism=1`       |
+| `tfapp` | `terraform apply tfplan`               |
 | `tfc`   | `terraform console`                    |
 | `tfd`   | `terraform destroy`                    |
 | `tfd!`  | `terraform destroy -auto-approve`      |
@@ -33,6 +34,7 @@ plugins=(... terraform)
 | `tfiur` | `terraform init -upgrade -reconfigure` |
 | `tfo`   | `terraform output`                     |
 | `tfp`   | `terraform plan`                       |
+| `tfpo`  | `terraform plan -out tfplan`           |
 | `tfv`   | `terraform validate`                   |
 | `tfs`   | `terraform state`                      |
 | `tft`   | `terraform test`                       |

plugins/terraform/terraform.plugin.zsh

@@ -1,3 +1,8 @@
+# Return immediately if terraform is not found
+if (( ! ${+commands[terraform]} )); then
+  return
+fi
+
 function tf_prompt_info() {
   # dont show 'default' workspace in home dir
   [[ "$PWD" != ~ ]] || return