test(rectification): type the read-case tool cast in the BUG-1057 test (T3 follow-up)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017eEAG8HD3mm8gsKXgk8uU8

frontend/tests/rectification-grounding-read-case-20260927.test.ts

@@ -71,7 +71,7 @@ async function readCaseFor(turns: unknown[]) {
       turnId: TURN_ID,
       userMessage: "2014 年结婚",
       accounting: accounting.client as never,
-    }) as Record<string, { execute(input: unknown): Promise<Record<string, unknown>> }>;
+    }) as unknown as Record<string, { execute(input: unknown): Promise<Record<string, unknown>> }>;
     const readCase = await tools["rectification-read-case"].execute({ caseId: CASE_ID });
     return { readCase, candidateCount: latest.candidates.length };
   } finally {