fix: resolve TS2367 — view toggle active class in compact-only branch

The toggle only renders inside the compact branch, so viewMode is
always 'compact' there. Use static class assignment instead of a
comparison TypeScript correctly flags as unreachable.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/AgentHealth/AgentHealth.tsx

@@ -706,14 +706,14 @@ export default function AgentHealth() {
         <div className={styles.viewToolbar}>
           <div className={styles.viewToggle}>
             <button
-              className={`${styles.viewToggleBtn} ${viewMode === 'compact' ? styles.viewToggleBtnActive : ''}`}
+              className={`${styles.viewToggleBtn} ${styles.viewToggleBtnActive}`}
               onClick={() => toggleViewMode('compact')}
               title="Compact view"
             >
               <LayoutGrid size={14} />
             </button>
             <button
-              className={`${styles.viewToggleBtn} ${viewMode === 'expanded' ? styles.viewToggleBtnActive : ''}`}
+              className={styles.viewToggleBtn}
               onClick={() => toggleViewMode('expanded')}
               title="Expanded view"
             >