test(mcp): type the registration mocks by their signature, not an unused parameter

The mocks in the test of an arm that serves no engine named a parameter only to type their calls, which ESLint reports as unused; they now pass the signature to mock as other tests do.

Author: cevheri

tests/unit/mcp/statement-arms.test.ts

@@ -1401,18 +1401,18 @@ describe("the tool each engine is read with", () => {
       mongo: idle,
     } as unknown as typeof MCP_STATEMENT_ARMS;
     expect(servingStatementArms(arms)).toEqual([RUN_READ_QUERY_ARM]);
-    const registerTool = mock((_name: string) => undefined);
+    const registerTool = mock<(name: string) => undefined>(() => undefined);
     registerStatementTools({ registerTool } as unknown as McpServer, {} as McpConnectionContext, undefined, arms);
     expect(registerTool.mock.calls.map(([name]) => name)).toEqual(["run_read_query"]);
-    const reachMongo = mock((_name: string) => undefined);
+    const reachMongo = mock<(name: string) => undefined>(() => undefined);
     registerStatementTools(
       { registerTool: reachMongo } as unknown as McpServer,
       {} as McpConnectionContext,
       new Set(["mongodb"]),
       arms,
     );
     expect(reachMongo.mock.calls).toEqual([]);
-    const reachSqlite = mock((_name: string) => undefined);
+    const reachSqlite = mock<(name: string) => undefined>(() => undefined);
     registerStatementTools(
       { registerTool: reachSqlite } as unknown as McpServer,
       {} as McpConnectionContext,