REPORT: keep the description from turning into a heading

The pre-filled issue body put a `---` line right under the description,
which Markdown reads as a setext heading underline whenever text is typed
on the line above it. Use `***` instead.

Refs #1834

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/commands/view.rs

@@ -319,10 +319,12 @@ impl OpenCADStudio {
 
             "REPORT" => {
                 // Pre-fill the GitHub issue body with version + platform so
-                // reports arrive with the basics already filled in.
+                // reports arrive with the basics already filled in. The rule
+                // is `***`: text typed right above a `---` line turns into a
+                // Markdown heading.
                 let body = format!(
                     "<!-- Describe the issue and the steps to reproduce it. -->\n\n\n\
-                     ---\n- Open CAD Studio: v{}\n- Revision: {} ({}, {})\n- Platform: {}\n",
+                     ***\n- Open CAD Studio: v{}\n- Revision: {} ({}, {})\n- Platform: {}\n",
                     env!("OCS_FULL_VERSION"),
                     env!("OCS_GIT_REV"),
                     env!("OCS_COMMIT_DATE"),