Add diagnostic scan cross-check of the Hermes counters -- FABRIC-3.6.md task 2.8

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/starkernel/vm/kernel_hermes.c

@@ -88,6 +88,24 @@ uint64_t sk_hermes_audit_failure_count(void) {
     return sk_hermes_audit_failures;
 }
 
+uint64_t sk_hermes_scan_held(size_t *live_count) {
+    uint64_t sum = 0;
+    size_t n = 0;
+    int i;
+
+    for (i = 0; i < SK_HERMES_MSG_MAX; i++) {
+        if (!sk_hermes_msgs[i].in_use || sk_hermes_msgs[i].stadium_cell < 0) continue;
+        sum += stadium_cells()[sk_hermes_msgs[i].stadium_cell].header.heat;
+        n++;
+    }
+    if (live_count) *live_count = n;
+    return sum;
+}
+
+int sk_hermes_scan_check(void) {
+    return sk_hermes_scan_held((size_t *)0) == sk_hermes_held;
+}
+
 static int sk_hermes_find_free_slot(void) {
     int i;
     for (i = 0; i < SK_HERMES_MSG_MAX; i++) {