fix(KB-083): fix SpecEditor layout with proper CSS and remove hardcoded rows

- Add comprehensive CSS styles for SpecEditor component layout
- Remove hardcoded rows prop from SpecEditor for flexible sizing
- Add layout tests for SpecEditor to verify responsive behavior
- Include changeset for patch release of @dustinbyrne/kb package

packages/dashboard/app/components/SpecEditor.tsx

@@ -128,7 +128,6 @@ export function SpecEditor({
             onChange={(e) => setEditContent(e.target.value)}
             disabled={isSaving}
             placeholder="Enter task specification in Markdown..."
-            rows={20}
           />
         ) : content ? (
           <div className="markdown-body">