fix(integrations): address code-review findings

n8n: throw on FAILED memory events (was silently returned), poll on any
non-terminal status (PENDING or RUNNING), use top_k (not limit) for
search, coerce search/getAll responses to arrays, guard invalid-JSON
metadata, reject empty updates, mark user_id required; lint clean.

Zapier: coerce boolean fields (String(x) !== 'false') + boolean defaults
so "Wait"/"Infer = No" are honored, throw on HTTP >= 400 (was silent
empty/fake-success), throw on FAILED events, use top_k, numeric coercion
with clamping, mark user_id required.

integrations/zapier-mem0/test/mem0.test.js

@@ -66,4 +66,14 @@ describe('Mem0 Zapier integration (E2E)', () => {
 		});
 		expect(afterDelete.length).toBe(0);
 	});
+
+	it('surfaces API errors instead of returning an empty array (search needs a filter)', async () => {
+		// filters is required by the API; omitting it must throw, not return [].
+		await expect(
+			appTester(App.searches.search_memories.operation.perform, {
+				authData,
+				inputData: { query: 'anything' },
+			}),
+		).rejects.toThrow();
+	});
 });