fix: allow closing terminal chart slots

frontend/components/dashboard/scan-terminal/__tests__/terminalGridPolicy.test.ts

@@ -57,6 +57,16 @@ export function runTests() {
       dashboardSource.includes("disableClose={true}"),
     "mobile terminal should render one selected chart and suggest landscape for the full grid",
   );
+  assert(
+    !dashboardSource.includes("disableClose={visibleSlots.filter(Boolean).length <= 1}"),
+    "desktop chart slots must allow clearing the last visible city so users can close a 1x1 chart",
+  );
+  assert(
+    dashboardSource.includes("readStoredTerminalSlots") &&
+      dashboardSource.includes("hasPersistedSlots") &&
+      dashboardSource.includes("shouldAutofillInitialSlots"),
+    "terminal slots must distinguish first-load default fill from a user-cleared all-empty layout",
+  );
   assert(
     selectorSource.includes("[1, 2, 3].map") &&
       selectorSource.includes("grid grid-cols-3"),