Switch language in place, without a reload

Choosing a language in the picker now applies it at once. The choice is
stored and ?lang is kept in step through replaceState, and the picker keeps
focus.

Code that writes translated text itself re-presents it on a switch:
onLocaleChange() lets an owner listen, removed at teardown, and status
writers hand over a function of the locale (voice cards, scene director,
SDR, draw hints, imagery split, map sources, Bhote Koshi media) so the
words are rebuilt rather than re-sent. The HUD, cockpit, radio, CCTV,
launch, awareness and credit texts follow the same hook, and
applyDocumentTranslations can be applied again without undoing text code
wrote since.

The unsaved-work registry and persistLocaleAndReload existed only to guard
the reload, so they go, with their catalog entries.

src/i18n/locales/fr.json

@@ -11,7 +11,6 @@
   "That line has no length — click somewhere further away.": "Cette ligne n'a pas de longueur — cliquez plus loin.",
   " · {max}-point limit reached": " · limite de {max} points atteinte",
   "{measure} · double-click or Enter to finish, Backspace undoes, Esc cancels.{full}": "{measure} · double-clic ou Enter pour terminer, Backspace annule le dernier point, Esc annule.{full}",
-  "drawings on the map": "les dessins sur la carte",
   "That shape already has {count} points — finish it or press Backspace.": "Cette forme a déjà {count} points — terminez-la ou appuyez sur Backspace.",
   "That point is off the globe — click on the world.": "Ce point est hors du globe — cliquez sur la Terre.",
   "That shape could not be placed.": "Impossible de placer cette forme.",
@@ -402,7 +401,6 @@
   "paste {envVar}": "collez {envVar}",
   "REMOVE": "SUPPRIMER",
   "Remove {title} from this app's saved keys": "Supprimer {title} des clés enregistrées de l'application",
-  "unsaved provider keys": "les clés de fournisseurs non enregistrées",
   "Project keys: {status}": "Clés du projet : {status}",
   "your app configuration": "la configuration de votre application",
   "your local .env": "votre .env local",
@@ -1540,9 +1538,6 @@
   "Sensitivity": "Sensibilité",
   "WHOT/BHOT": "WHOT/BHOT",
   "Ironbow": "Ironbow",
-  "unsaved CCTV calibration": "la calibration CCTV non enregistrée",
-  "the open cockpit": "le cockpit ouvert",
-  "Switching language reloads the page. This will be lost: {items}. Switch anyway?": "Changer de langue recharge la page. Ceci sera perdu : {items}. Changer quand même ?",
   "VISUAL PRESETS": "PRÉRÉGLAGES VISUELS",
   "LOCATION": "LIEU",
   "CONTACTS — nearest planes · vessels · sites": "CONTACTS — avions, navires et sites les plus proches",
@@ -1767,7 +1762,6 @@
   "Space Missions": "Missions spatiales",
   "Context": "Contexte",
   "Rendered globe frames per second · toggle with `": "Images du globe rendues par seconde · basculer avec `",
-  "imported map files": "les fichiers importés sur la carte",
   "Ground heights could not be refreshed. Try the file again when the map has loaded.": "Impossible d'actualiser les altitudes du sol. Réessayez avec le fichier une fois la carte chargée.",
   "{count} map objects": {
     "one": "{count} objet cartographique",
@@ -2547,7 +2541,6 @@
   "Activate to toggle voice": "Activer/désactiver la commande vocale",
   "Voice active": "Voix active",
   "Voice could not be started.": "Impossible de démarrer la voix.",
-  "the active voice session": "la session vocale active",
   "{value} feet": "{value} pieds",
   "Fire · FRP {frp} MW": "Feu · FRP {frp} MW",
   "The flights layer is not enabled": "La couche des vols n'est pas activée",