fix(skills): keep file-prefix and label joined by template literal

Prettier reformats JSX into one expression per line; splitting
"{file.prefix}{file.label}" across two lines inserts a literal
whitespace text node between them. Snapshot diff against
.agents/snapshots/skills.txt showed the rendered HTML emitted
"├──  SKILL.md" (two spaces) where vanilla showed one. Joining
the values into a single template expression keeps the rendered
text byte-identical to the legacy source.

src/components/islands/SkillPackageExplorer.astro

@@ -73,10 +73,7 @@ const packageFiles: PackageFile[] = [
           role="tab"
           aria-selected={String(index === 0)}
         >
-          <code>
+          <code>{`${file.prefix}${file.label}`}</code>
-            {file.prefix}
-            {file.label}
-          </code>
           <small>{file.caption}</small>
         </button>
       ))