Support skills shortDescription. (#8278)

Allow SKILL.md to specify a more human-readable short description as
skill metadata.

codex-rs/tui2/src/bottom_pane/skill_popup.rs

@@ -86,7 +86,11 @@ impl SkillPopup {
                     .and_then(|n| n.to_str())
                     .unwrap_or(&skill.name);
                 let name = format!("{} ({slug})", skill.name);
-                let description = skill.description.clone();
+                let description = skill
+                    .short_description
+                    .as_ref()
+                    .unwrap_or(&skill.description)
+                    .clone();
                 GenericDisplayRow {
                     name,
                     match_indices: indices,