feat(cluster): county and prefix get their chase switches, and the grid one tells the whole truth

Chase POTA already withdrew its badge, filter chip and column when
unchecked; US counties and new prefixes now have the same switch, and
unchecking Chase new grids finally withdraws the NEW GRID badge too (the
backend stopped learning squares but the display kept shouting the ones
it knew — the setting is mirrored to localStorage so the display layer
can gate synchronously). All withdrawal happens at the display layer:
the facts keep being computed, so re-ticking a box needs no rescan.

frontend/src/App.tsx

@@ -100,7 +100,7 @@ import { ExportFieldsDialog } from '@/components/ExportFieldsDialog';
 import { ShutdownProgress } from '@/components/ShutdownProgress';
 import { ClusterGrid } from '@/components/ClusterGrid';
 import { cleanSpotter, inferSpotMode, spotModeCategory, spotStatusKey } from '@/lib/spot';
-import { applySpotDisplay, chasePota, readSpotDisplayOptions, spotIsWorked, SPOT_DISPLAY_OPTIONS_EXPOSED } from '@/lib/spotDisplay';
+import { applySpotDisplay, chaseCounty, chaseGrid, chasePfx, chasePota, readSpotDisplayOptions, spotIsWorked, SPOT_DISPLAY_OPTIONS_EXPOSED } from '@/lib/spotDisplay';
 import { AnswerDecode, HaltDecodeTx, LogUIError, FlexTXOnBand, GetMatrixColors, GetRotorPresets, GetRowColors, GetSpotTTLMinutes, GetSpotMax, IsNewUSCounty } from '../wailsjs/go/main/App';
 import { applyMatrixColors } from '@/lib/matrixColors';
 import { WorkedBeforeGrid } from '@/components/WorkedBeforeGrid';
@@ -6261,7 +6261,10 @@ export default function App() {
               // worked spots; the separate "Hide worked" checkbox drops them — they
               // are opposite controls, so don't use both at once.
               { k: 'worked'   as SpotFilterKey, label: 'WORKED',   cls: 'bg-info-muted text-info-muted-foreground border-info-border' },
-            ]).filter((s: any) => s.k !== 'new-pota' || chasePota())
+            ]).filter((s: any) => (s.k !== 'new-pota' || chasePota())
+              && (s.k !== 'new-county' || chaseCounty())
+              && (s.k !== 'new-pfx' || chasePfx())
+              && (s.k !== 'new-grid' || chaseGrid()))
               .map((s: any) => fChip(s.k, s.label, s.cls, clusterStatusFilter.has(s.k),
               () => setClusterStatusFilter((cur) => { const n = new Set(cur); if (n.has(s.k)) n.delete(s.k); else n.add(s.k); return n; }), s.style))}
           </div>,