Fix isPlatformError check: use instanceof instead of Predicate.isTagged

Predicate.isTagged(u, 'PlatformError') checks u._tag === 'PlatformError', but
PlatformError is a union of BadArgument (_tag: 'BadArgument') and SystemError
(_tag: 'SystemError'), so the check never matched. This silently broke the
AlreadyExists race-condition recovery in getOrCreateRandom.

Use 'instanceof PlatformError.PlatformError' instead, consistent with the
existing check in the remove function.

Author: cursoragent

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

@@ -1,6 +1,6 @@
 import * as Crypto from "node:crypto";
 
-import { Effect, FileSystem, Layer, Path, Predicate } from "effect";
+import { Effect, FileSystem, Layer, Path } from "effect";
 import * as PlatformError from "effect/PlatformError";
 
 import { ServerConfig } from "../../config.ts";
@@ -28,9 +28,6 @@ export const makeServerSecretStore = Effect.gen(function* () {
 
   const resolveSecretPath = (name: string) => path.join(serverConfig.secretsDir, `${name}.bin`);
 
-  const isPlatformError = (u: unknown): u is PlatformError.PlatformError =>
-    Predicate.isTagged(u, "PlatformError");
-
   const get: ServerSecretStoreShape["get"] = (name) =>
     fileSystem.readFile(resolveSecretPath(name)).pipe(
       Effect.map((bytes) => Uint8Array.from(bytes)),
@@ -105,7 +102,8 @@ export const makeServerSecretStore = Effect.gen(function* () {
         return create(name, generated).pipe(
           Effect.as(Uint8Array.from(generated)),
           Effect.catchTag("SecretStoreError", (error) =>
-            isPlatformError(error.cause) && error.cause.reason._tag === "AlreadyExists"
+            error.cause instanceof PlatformError.PlatformError &&
+            error.cause.reason._tag === "AlreadyExists"
               ? get(name).pipe(
                   Effect.flatMap((created) =>
                     created !== null