fix(installing-roxctl-cli): Add DITA short description

- Added [role="_abstract"] marker to introductory paragraph

Fixes AsciiDocDITA.ShortDescription issue at line 7

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

Author: Agil Antony

modules/installing-the-roxctl-cli.adoc

@@ -6,4 +6,5 @@
 [id="installing-roxctl-cli-sc-other"]
 = Install the roxctl CLI
 
+[role="_abstract"]
 You must first download the binary. You can install `roxctl` on Linux, Windows, or macOS.