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>

include/starkernel/vm/kernel_hermes.h

@@ -264,6 +264,21 @@ int sk_hermes_audit_values(uint64_t held, uint64_t pulled, uint64_t returned, ui
 int sk_hermes_audit(void);
 uint64_t sk_hermes_audit_failure_count(void);
 
+/*
+ * Task 2.8 (item 28), SXXXVII.4: the scan that verifies the counters
+ * themselves. DIAGNOSTIC ONLY -- O(SK_HERMES_MSG_MAX), never called from
+ * alloc/release/decay.
+ *
+ * sk_hermes_scan_held - walks the message arena and sums the live Stadium
+ * cell heat of every in-use message (the ground truth `held` claims to
+ * track). Sets *live_count (may be NULL) to the messages counted.
+ *
+ * sk_hermes_scan_check - nonzero iff the scan sum equals the `held`
+ * counter exactly.
+ */
+uint64_t sk_hermes_scan_held(size_t *live_count);
+int sk_hermes_scan_check(void);
+
 #endif /* __STARKERNEL__ */
 
 #endif /* STARKERNEL_VM_KERNEL_HERMES_H */