fix(test): convert forbidden SKIP()s in the complexity suite to policy forms

The no-skips lint gate (scripts/check-no-test-skips.sh) rightly rejected the
throughput-report test's two SKIP() calls:

- CBM_SKIP_PERF=1 is deliberate operator configuration, not a hidden
  environment failure: reporting is off by request, so the test PASSes with a
  stderr note instead of skipping.
- an uncreatable report dir IS an environment failure and now FAILs with the
  remedy in the message (set CBM_COMPLEXITY_REPORT_DIR), per the policy text.

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

tests/test_complexity.c

@@ -609,7 +609,12 @@ TEST(complexity_shared_package_growth_stays_linear) {
 TEST(complexity_throughput_report_written) {
     const char *skip_perf = getenv("CBM_SKIP_PERF");
     if (skip_perf && skip_perf[0] == '1') {
-        SKIP("CBM_SKIP_PERF: throughput rates are meaningless under CPU starvation");
+        /* Deliberate operator config, not a hidden environment failure
+         * (no-skips policy): rates measured under CBM_SKIP_PERF starvation
+         * would only mislead, so reporting is OFF and there is nothing left
+         * for this test to assert. */
+        fprintf(stderr, "  [complexity] CBM_SKIP_PERF=1: throughput report disabled by config\n");
+        PASS();
     }
     if (cx_measure_pair() != 0) {
         FAIL("failed to build/run the complexity corpus pair");
@@ -619,7 +624,7 @@ TEST(complexity_throughput_report_written) {
         dir = "private/benchmarks";
     }
     if (th_mkdir_p(dir) != 0) {
-        SKIP("report dir not creatable here (read-only checkout?)");
+        FAIL("report dir not creatable (set CBM_COMPLEXITY_REPORT_DIR to a writable path)");
     }
     char path[1024];
     snprintf(path, sizeof(path), "%s/complexity-%lld.json", dir, (long long)time(NULL));