Filter accounts on @type, the name Stalwart uses

The Accounts list sent x:Account/query with {"type": "User"}, and a live
0.16 server refuses it: "unsupportedFilter - type". The registry keys a
filter by the property's name on the object, which for the discriminator is
@type, so the whole list failed to load. {"@type": "User"} is accepted.

The mock took the wrong name without complaint, which is how it shipped. It
now refuses any filter name the real server does not index for that object,
answering the way Stalwart does.

web/src/lib/__tests__/adminDirectory.test.ts

@@ -1,5 +1,6 @@
-import { describe, expect, it } from "vitest";
-import { aliasList, describeDirectoryError, DirectoryError, hasPassword, passwordPatch, quotasWithDisk } from "@/lib/adminDirectory";
+import { describe, expect, it, vi } from "vitest";
+import { client } from "@/jmap/client";
+import { aliasList, describeDirectoryError, DirectoryError, hasPassword, passwordPatch, queryAccounts, quotasWithDisk } from "@/lib/adminDirectory";
 
 describe("setting a password", () => {
   it("writes into the existing password credential, keeping its place", () => {
@@ -43,3 +44,14 @@ describe("explaining a refusal", () => {
     expect(describeDirectoryError({ type: "forbidden", message: "x:Account/set: forbidden" })).toMatch(/refused/);
   });
 });
+
+describe("the account query", () => {
+  it("filters on @type, the property's name on the object", async () => {
+    // A live 0.16 server answers a plain `type` with "unsupportedFilter - type"
+    // and fails the whole list, which is how this was found.
+    const call = vi.spyOn(client, "call").mockResolvedValue({ ids: [], total: 0 });
+    await queryAccounts({ type: "User", text: " ada ", position: 50, limit: 50 });
+    expect(call).toHaveBeenCalledWith("x:Account/query", { filter: { "@type": "User", text: "ada" }, position: 50, limit: 50, calculateTotal: true });
+    call.mockRestore();
+  });
+});