test(cli): restore Pi abort-kill assertion dropped alongside #2787 test

The #2787 change added client_adapter_pi_emits_string_enum_issue2787 directly below client_adapter_pi_wraps_result_and_honors_abort and, in the same hunk, removed that test's check that the generated abort handler kills the cli child (if (!child.killed) child.kill();). The generator still emits the line; restore the assertion byte-for-byte so the abort path keeps its coverage.

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

tests/test_agent_clients.c

@@ -1243,6 +1243,7 @@ TEST(client_adapter_pi_wraps_result_and_honors_abort) {
     ASSERT_NOT_NULL(
         strstr(js, "[{ type: 'text', text: JSON.stringify(result ?? null, null, 2) }]"));
     ASSERT_NOT_NULL(strstr(js, "signal?.addEventListener('abort', onAbort, { once: true })"));
+    ASSERT_NOT_NULL(strstr(js, "if (!child.killed) child.kill();"));
     free(js);
     PASS();
 }