feat(cluster): mark the cell that carries the fact, and add the US county

Colour moves from the text to the CELL. A filled Band cell means new band, a
filled Pfx cell means new prefix, a filled County cell means new county. This is
not the pills coming back: a pill is a box inside the cell with its own height
and padding, so it pushed the text off the row baseline. A background has no
geometry - the text does not move a pixel - and it reads from across the room,
which a tinted glyph does not. Worked-call stays text-only: it is not a novelty,
and filling it would wash most of the rows.

The colours still come from the semantic tokens and lib/spotMarkers, so a fact
keeps one colour across the grid, the band map and the filter chips - and the
per-marker colour setting will drive all of it from one table.

US County column. The backend already resolved the county from the offline ULS
store to decide NewCounty and then threw it away; it now returns it, which costs
nothing.

The Locator column is renamed Spotter locator. It always held the SPOTTER's grid
- cluster.go says so - so a column labelled Locator next to a DX callsign was
reading as the DX's grid and was mostly empty besides. The DX grid is not in the
feed at any price worth paying under an RBN firehose.

Both display options move out of Preferences into the cluster filter panel,
beside Hide worked. They are changed while working a run, not set up once, and
a preferences dialog reopened every ten minutes is a filter in the wrong place.

app.go

@@ -16394,7 +16394,12 @@ type SpotStatus struct {
 	// is resolved from the callsign via the offline ULS store (US only, and only
 	// when that database has been downloaded); POTA from the spot's tagged park.
 	NewCounty bool `json:"new_county"`
-	NewPOTA   bool `json:"new_pota"`
+	// County and State are that resolved county, so the cluster can show it as a
+	// column instead of only flagging it. Free: the ULS lookup that decides
+	// NewCounty already has them in hand.
+	County  string `json:"county,omitempty"`
+	State   string `json:"state,omitempty"`
+	NewPOTA bool   `json:"new_pota"`
 	// NewPfx flags a CQ WPX prefix never worked before, and Pfx is that prefix.
 	// Also orthogonal: a common entity on a worked band can still carry a prefix
 	// that has never been in the log, which is exactly what a WPX chaser is
@@ -16580,6 +16585,7 @@ func (a *App) ClusterSpotStatuses(spots []SpotQuery) []SpotStatus {
 		// store (US only; inert until downloaded) and flag if never worked.
 		if a.uls != nil {
 			if loc, ok := a.uls.Resolve(q.Call); ok {
+				out[i].County, out[i].State = loc.County, loc.State
 				if key := award.USCountyKey(loc.State, loc.County); key != "" {
 					if _, done := workedCounties[key]; !done {
 						out[i].NewCounty = true