migrate pure-logic tests to vitest (phase 1)

vitest/mmkv-stub.ts

@@ -0,0 +1,24 @@
+/*
+ * Stub for @bsky.app/react-native-mmkv. The real package binds to a native
+ * module and imports `react-native`, neither of which works under Vitest's
+ * node environment. Tests that exercise storage logic mock this module's MMKV
+ * with their own in-memory implementation; this stub just provides a class
+ * shape so transitive importers (e.g. #/storage) load without booting RN.
+ *
+ * Aliased in place of @bsky.app/react-native-mmkv via resolve.alias in
+ * vitest.config.ts.
+ */
+export class MMKV {
+  getString() {
+    return undefined
+  }
+  set() {}
+  delete() {}
+  getAllKeys(): string[] {
+    return []
+  }
+  clearAll() {}
+  addOnValueChangedListener() {
+    return {remove() {}}
+  }
+}