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.

changelog.json

@@ -4,11 +4,13 @@
     "date": "",
     "en": [
       "Band openings: OpsLog now tells you when 6, 4 or 2 m opens. It watches the spots already arriving from your clusters and RBN — several different stations appearing at single-hop range (500–2400 km) in the same bearing sector within a few minutes is the signature of sporadic E, and nothing else looks like it. You get one message per band per opening, naming the sector and the typical distance. An opening outside the usual season is still announced, and flagged as unusual: those are the ones worth knowing about. Nothing to configure — but the quality depends on having a cluster or RBN feed carrying VHF spots, and 2 m openings are often worked without ever being spotted.",
-      "DX cluster, two display options (Settings › DX cluster). The first drops the colour and the badges on stations you have already worked: they stay in the list, they simply stop competing for your attention. The second colours every callsign you have not worked on this band and this mode, even when the entity itself is long since confirmed — the view for filling slots rather than chasing new ones. Both apply to the cluster list and to the band map, so the two panels always agree."
+      "DX cluster, two display options (Settings › DX cluster). The first drops the colour and the badges on stations you have already worked: they stay in the list, they simply stop competing for your attention. The second colours every callsign you have not worked on this band and this mode, even when the entity itself is long since confirmed — the view for filling slots rather than chasing new ones. Both apply to the cluster list and to the band map, so the two panels always agree.",
+      "DX cluster, clearer at a glance. A novelty now FILLS the cell that carries it — a filled Band cell means new band, a filled Pfx cell means new prefix, a filled County cell means new county — instead of only tinting the text. A US County column joins the list, resolved offline from the ULS database. The station-not-worked-here highlight is its own NEW CALL status with its own filter chip, no longer borrowed from NEW SLOT, which means something narrower. The two display options moved from Preferences into the cluster filter panel, next to Hide worked. The Locator column is now labelled Spotter locator, because that is what a cluster line actually carries."
     ],
     "fr": [
       "Ouvertures de bande : OpsLog te signale désormais l ouverture du 6, du 4 ou du 2 m. Il surveille les spots qui arrivent déjà de tes clusters et du RBN — plusieurs stations différentes apparaissant à distance de saut simple (500–2400 km) dans le même secteur d azimut en quelques minutes, c est la signature de l Es, et rien d autre n y ressemble. Un message par bande et par ouverture, avec le secteur et la distance typique. Une ouverture hors saison est annoncée quand même, et signalée comme inhabituelle : ce sont celles qu il ne faut surtout pas manquer. Rien à configurer — mais la qualité dépend d avoir un flux cluster ou RBN qui porte des spots VHF, et les ouvertures 2 m sont souvent travaillées sans jamais être spottées.",
-      "Cluster DX, deux options d affichage (Paramètres › Cluster DX). La première enlève la couleur et les badges sur les stations déjà contactées : elles restent dans la liste, elles cessent simplement d attirer l œil. La seconde colore tout indicatif non contacté sur cette bande et ce mode, même si l entité est confirmée depuis longtemps — la vue pour remplir des slots plutôt que pour chasser du nouveau. Les deux s appliquent à la liste cluster et au bandmap, les deux panneaux restent donc cohérents."
+      "Cluster DX, deux options d affichage (Paramètres › Cluster DX). La première enlève la couleur et les badges sur les stations déjà contactées : elles restent dans la liste, elles cessent simplement d attirer l œil. La seconde colore tout indicatif non contacté sur cette bande et ce mode, même si l entité est confirmée depuis longtemps — la vue pour remplir des slots plutôt que pour chasser du nouveau. Les deux s appliquent à la liste cluster et au bandmap, les deux panneaux restent donc cohérents.",
+      "Cluster DX, plus lisible d un coup d œil. Une nouveauté REMPLIT désormais la cellule qui la porte — cellule Bande remplie = nouvelle bande, cellule Préf. remplie = nouveau préfixe, cellule Comté remplie = nouveau comté — au lieu de seulement colorer le texte. Une colonne Comté US rejoint la liste, résolue hors ligne depuis la base ULS. La mise en couleur des stations non contactées ici devient un statut CALL NEUF à part entière, avec sa propre puce de filtre, au lieu d emprunter NOUV SLOT qui veut dire autre chose. Les deux options d affichage passent des Préférences au panneau de filtres du cluster, à côté de Hide worked. La colonne Locator s appelle maintenant Locator du spotter, puisque c est ce qu une ligne de cluster porte réellement."
     ]
   },
   {