Drop Snow from the new catalogs and migrate saved Snow shots

The it, pt and uk catalogs merged from main still carried the two Snow
button strings, which the catalog tests report as stale. They are
pruned with npm run i18n -- --prune.

A Scene Director shot saved with Snow now normalizes to Normal when the
project loads, so the shot list shows NORMAL rather than an untranslated
SNOW for a shot that plays on Normal. The README's style keys read 1-6.

scripts/package-boundaries.json

@@ -964,7 +964,8 @@
       "src/i18n/locales/uk.json",
       "src/i18n/locales/zh-CN.json",
       "src/i18n/locales/zh-Hant.json",
-      "src/ui/unitLabels.js"
+      "src/ui/unitLabels.js",
+      "src/visualStylePolicy.js"
     ],
     "external": ["cesium"]
   },