fix(contracts): make AuthAccessStreamError wire-compatible across versions

The schema changed from { message } to { operation, cause } without
backward compatibility, breaking schema decoding when client and server
versions are mismatched during rolling deployments.

Follow the same pattern as EnvironmentHttpInternalServerError:
- Keep message: Schema.String in the schema (always on the wire)
- Make operation optional for decode (old payloads only have message)
- Remove cause from the schema (avoid exposing internal errors)
- Use a custom constructor that requires operation and computes message

Author: cursoragent

packages/contracts/src/auth.ts

@@ -285,15 +285,29 @@ export type AuthAccessStreamOperation = typeof AuthAccessStreamOperation.Type;
 export class AuthAccessStreamError extends Schema.TaggedErrorClass<AuthAccessStreamError>()(
   "AuthAccessStreamError",
   {
-    operation: AuthAccessStreamOperation,
+    operation: Schema.optional(AuthAccessStreamOperation),
     currentSessionId: Schema.optional(AuthSessionId),
-    cause: Schema.Defect(),
+    message: Schema.String,
   },
 ) {
-  override get message(): string {
+  // @effect-diagnostics-next-line overriddenSchemaConstructor:off
+  constructor(props: {
+    readonly operation: AuthAccessStreamOperation;
+    readonly currentSessionId?: string | undefined;
+    readonly cause?: unknown;
+  }) {
     const session =
-      this.currentSessionId === undefined ? "" : ` for session ${this.currentSessionId}`;
-    return `Authentication access stream operation ${this.operation} failed${session}.`;
+      props.currentSessionId === undefined ? "" : ` for session ${props.currentSessionId}`;
+    const message =
+      "message" in props && typeof (props as any).message === "string"
+        ? (props as any).message
+        : `Authentication access stream operation ${props.operation} failed${session}.`;
+    super({
+      operation: props.operation,
+      ...(props.currentSessionId === undefined ? {} : { currentSessionId: props.currentSessionId }),
+      message,
+      ...(props.cause === undefined ? {} : { cause: props.cause }),
+    } as any);
   }
 }