test(runtime): type the findOne options bag instead of casting it (#7537)

check:query-options-erasure counted the `as any` on the new findOne case as a
new untyped-options site (test surface 249 → 250). The input is on-contract —
`where` + `expand` are both `EngineQueryOptions` members — so the cast was
noise, not a deliberate contract bypass. Removing it satisfies the ratchet the
way the check asks for (type the options) rather than by spending the
`as unknown as EngineQueryOptions` escape hatch, which is reserved for tests
that must build genuinely off-contract input.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HJVZqLviCkZMJV8Nh3DUao

Author: claude

packages/runtime/src/expand-nested-fields-join-key.integration.test.ts

@@ -152,7 +152,7 @@ describe('#7537 expand with a nested `fields` that omits the join key (REAL SqlD
     const row: any = await e.findOne('showcase_invoice', {
       where: { id: inv.id },
       expand: { account: { object: 'showcase_account', fields: ['name'] } },
-    } as any);
+    });
 
     expect(row.account).toEqual({ name: 'Acme' });
   });