fix: use isPlatformError helper in remove() instead of instanceof check

Replace 'cause instanceof PlatformError.PlatformError' with
'isPlatformError(cause)' in the remove method for consistency with
the rest of the file and to avoid instanceof fragility across
module boundaries.

Author: cursoragent

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

@@ -126,7 +126,7 @@ export const makeServerSecretStore = Effect.gen(function* () {
   const remove: ServerSecretStoreShape["remove"] = (name) =>
     fileSystem.remove(resolveSecretPath(name)).pipe(
       Effect.catch((cause) =>
-        cause instanceof PlatformError.PlatformError && cause.reason._tag === "NotFound"
+        isPlatformError(cause) && cause.reason._tag === "NotFound"
           ? Effect.void
           : Effect.fail(
               new SecretStoreError({