fix(v3): the DoE row's cache and bucket hits are measured, not written as 0 (#142)

Captain Bob, 2026-11-12: "correct deficiencies". heartbeat_capture_tick_snapshot
wrote cache_hits_delta and bucket_hits_delta as 0 ("TODO: wire ..."), though
physics_hotwords_cache.c counts both. Now each is read from the VM's hot-words
cache as a delta since the previous tick, the way word_executions_delta is
(and after the cache's stats are reset, the count since then); a VM with no
cache has 0. word_executions_delta was measured already: doe_log.c's "TODO: 0"
for it was stale, and its three column notes are corrected.

kernel/tests/test_heartbeat_export.c, 4 checks: a VM in memory with a cache
whose counters the test sets, captured tick by tick. Against the code as it
was: 3 failures (the hits 0 where the cache counted 5 and 3, then 7 and 7).
Now: 0. Built for amd64, aarch64, riscv64 and the hosted v3. Shared v3 code,
under the ruling. v3 is not part of acceptance; no DoE has run since 2026-09-16.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017RzZgrf7V7Zk2iczBXDRbm

kernel/tests/Makefile

@@ -19,7 +19,8 @@ CC     ?= cc
 CFLAGS := -std=c99 -Wall -Wextra -Werror -O2 -g -I$(HERE) -I$(ROOT)/kernel/include \
           -I$(ROOT)/kernel/include/starkernel -I$(ROOT)/v3/include
 
-TESTS := test_gpt test_usb_config test_sk_v4_stop test_sk_v4_slots test_sk_v4_mint test_sk_v4_identity
+TESTS := test_gpt test_usb_config test_sk_v4_stop test_sk_v4_slots test_sk_v4_mint test_sk_v4_identity test_heartbeat_export
+SRC_test_heartbeat_export := $(ROOT)/v3/src/heartbeat_export.c
 SRC_test_sk_v4_identity := $(ROOT)/kernel/src/v4/sk_v4_identity.c $(ROOT)/kernel/src/v4/sk_v4_slots.c $(ROOT)/kernel/src/gpt.c
 EXTRA_test_sk_v4_identity := -D__STARKERNEL__ -I$(ROOT)/v4/include -DSTICK_GROW_MIN_BYTES=8000000000ULL -DSTICK_ARTEMIS_CAP_GIB=256ULL
 SRC_test_sk_v4_mint := $(ROOT)/kernel/src/v4/sk_v4_mint.c $(ROOT)/kernel/src/gpt.c

kernel/tests/test_heartbeat_export.c

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: LicenseRef-Starship-1.0
+ * Copyright (c) 2023-2026 Robert A. James
+ */
+/* test_heartbeat_export.c -- v3/src/heartbeat_export.c on the host (#142): the DoE row's per-tick
+ * deltas -- cache_hits_delta and bucket_hits_delta from the VM's hot-words cache, beside
+ * word_executions_delta -- are measured, not written as 0. A VM is built in memory with a cache
+ * whose hit counters the test sets, and heartbeat_capture_tick_snapshot is run tick by tick.
+ */
+#include "harness.h"
+#include "vm.h"
+#include "physics_hotwords_cache.h"
+#include <stdlib.h>
+#include <string.h>
+
+int main(void)
+{
+    VM *vm = (VM *)calloc(1, sizeof *vm);
+    HotwordsCache *cache = (HotwordsCache *)calloc(1, sizeof *cache);
+    HeartbeatTickSnapshot s;
+
+    vm->hotwords_cache = cache;
+
+    cache->stats.cache_hits = 5; cache->stats.bucket_hits = 3; vm->heartbeat.words_executed = 40;
+    memset(&s, 0, sizeof s); heartbeat_capture_tick_snapshot(vm, &s);
+    CHECK(s.cache_hits_delta == 5 && s.bucket_hits_delta == 3 && s.word_executions_delta == 40,
+          "#142: the first tick: 5 cache hits, 3 bucket hits, 40 words (%u, %u, %u)", s.cache_hits_delta, s.bucket_hits_delta, s.word_executions_delta);
+
+    cache->stats.cache_hits = 12; cache->stats.bucket_hits = 10; vm->heartbeat.words_executed = 100;
+    memset(&s, 0, sizeof s); heartbeat_capture_tick_snapshot(vm, &s);
+    CHECK(s.cache_hits_delta == 7 && s.bucket_hits_delta == 7 && s.word_executions_delta == 60,
+          "#142: the next tick: the deltas, 7, 7 and 60 (%u, %u, %u)", s.cache_hits_delta, s.bucket_hits_delta, s.word_executions_delta);
+
+    cache->stats.cache_hits = 2; cache->stats.bucket_hits = 1;          /* the cache's stats were reset */
+    memset(&s, 0, sizeof s); heartbeat_capture_tick_snapshot(vm, &s);
+    CHECK(s.cache_hits_delta == 2 && s.bucket_hits_delta == 1,
+          "#142: after the stats are reset, the count since then, as words_executed is (%u, %u)", s.cache_hits_delta, s.bucket_hits_delta);
+
+    vm->hotwords_cache = 0;
+    memset(&s, 0xFF, sizeof s); heartbeat_capture_tick_snapshot(vm, &s);
+    CHECK(s.cache_hits_delta == 0 && s.bucket_hits_delta == 0, "#142: a VM with no cache: 0 hits, not garbage");
+
+    free(cache); free(vm);
+    return DONE();
+}