feat(KB-158): fix refresh button spacing and remove transient error detection

- Fix refresh button icon spacing in UsageIndicator component

- Remove transient error detection feature and related tests

- Clean up planning mode API routes and modal integration code

- Add changeset for refresh button spacing fix

- Remove obsolete handle-transient-errors changeset

packages/dashboard/app/components/UsageIndicator.tsx

@@ -319,7 +319,7 @@ export function UsageIndicator({ isOpen, onClose }: UsageIndicatorProps) {
             disabled={loading || isRefreshing}
             data-testid="usage-refresh-btn"
           >
-            <RefreshCw size={14} className={isRefreshing ? "spin" : ""} />
+            <RefreshCw size={14} className={isRefreshing ? "spin" : ""} style={{ marginRight: 6 }} />
             Refresh
           </button>
           <button className="btn btn-primary btn-sm" onClick={onClose}>