cut over to vitest: drop jest config, deps, setup, update CI

eslint.config.mjs

@@ -197,8 +197,6 @@ export default defineConfig(
         'error',
         {
           whitelist: [
-            // test files only
-            '@jest/globals',
             // we only use a really simple util from this, and we know it will be present
             'expo-modules-core',
             // this is a dep for @atproto/api, but we absolutely need them in sync, so just
@@ -320,7 +318,6 @@ export default defineConfig(
     files: ['**/__tests__/**/*.{js,jsx,ts,tsx}', '**/*.test.{js,jsx,ts,tsx}'],
     languageOptions: {
       globals: {
-        ...globals.jest,
         ...globals.vitest,
       },
     },