fix: add missing isPlatformError type guard in ServerSecretStore.get

The get method was accessing cause.reason._tag without first checking if
cause is a PlatformError, which could throw a TypeError at runtime. This
adds the isPlatformError guard consistent with remove and getOrCreateRandom.

Author: cursoragent

apps/server/src/auth/Layers/ServerSecretStore.ts

@@ -35,7 +35,7 @@ export const makeServerSecretStore = Effect.gen(function* () {
     fileSystem.readFile(resolveSecretPath(name)).pipe(
       Effect.map((bytes) => Uint8Array.from(bytes)),
       Effect.catch((cause) =>
-        cause.reason._tag === "NotFound"
+        isPlatformError(cause) && cause.reason._tag === "NotFound"
           ? Effect.succeed(null)
           : Effect.fail(
               new SecretStoreError({