fix(goose2): keep model picker and session config in sync (#9048)

Signed-off-by: Matt Toohey <contact@matttoohey.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/goose2/src/shared/i18n/locales/en/chat.json

@@ -13,6 +13,9 @@
     "openPanel": "Open context panel",
     "ringAria": "Context: {{percent}}% used"
   },
+  "errors": {
+    "sessionPreparationSuperseded": "Session configuration changed while preparing. Try sending again."
+  },
   "contextPanel": {
     "actions": {
       "chooseCreateAction": "Choose create action",

ui/goose2/src/shared/i18n/locales/es/chat.json

@@ -13,6 +13,9 @@
     "openPanel": "Abrir panel de contexto",
     "ringAria": "Contexto: {{percent}}% usado"
   },
+  "errors": {
+    "sessionPreparationSuperseded": "La configuración de la sesión cambió durante la preparación. Intenta enviar de nuevo."
+  },
   "contextPanel": {
     "actions": {
       "chooseCreateAction": "Elegir acción de creación",