feat: add aria attributes to context utilization progress bar

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/components/InferenceStatsPanel.svelte

@@ -75,6 +75,11 @@
 					<div
 						class="h-full rounded-full transition-all duration-300 {utilizationColor.bar}"
 						style="width: {utilizationPct}%"
+						role="progressbar"
+						aria-valuenow={utilizationPct}
+						aria-valuemin={0}
+						aria-valuemax={100}
+						aria-label="Context window utilization"
 					></div>
 				</div>
 			</div>