reuse-configuration: convert UI/CLI subsections to tabs

Replace the H3 split between "In the Viam app" and "With the CLI" with a
{{< tabs >}} pair. Same content; tabs frame the two flows as alternatives.

Author: shannonbradshaw

docs/fleet/reuse-configuration.md

@@ -56,7 +56,8 @@ Click **Save** after adding and configuring your resources.
 
 ## Apply a fragment to a machine
 
-### In the Viam app
+{{< tabs >}}
+{{% tab name="Viam app" %}}
 
 1. Navigate to your machine's **CONFIGURE** tab.
 1. Click **+** and select **Configuration block**.
@@ -67,7 +68,8 @@ Click **Save** after adding and configuring your resources.
 
 The fragment's resources now appear on the machine's configuration page. The machine downloads and applies the configuration on its next sync.
 
-### With the CLI
+{{% /tab %}}
+{{% tab name="CLI" %}}
 
 ```sh {class="command-line" data-prompt="$"}
 viam machines part fragments add --part=<part-id> --fragment=<fragment-name-or-id>
@@ -79,6 +81,9 @@ If you omit `--fragment`, the CLI prompts you to pick a fragment interactively f
 
 To apply a fragment across many machines, see [Automate with scripts](/cli/automate-with-scripts/).
 
+{{% /tab %}}
+{{< /tabs >}}
+
 ### Avoid resource name conflicts with a prefix
 
 If a machine already has a resource with the same name as one in the fragment, or if you apply the same fragment twice, you need a prefix to avoid name collisions.