feat(log): LOG-FLUSH -- a VM's log records reach Artemis's log ring; and the ring keeps its order when it grows

FABRIC-3 SXXXII.4's deferred LOG-FLUSH, built to the 2026-10-14 rulings
(SXXXVIII): everything a VM logs, at or above the log level, goes into its
own buffer; it goes to Artemis on LOG-FLUSH, when full, and at once on an
ERROR, as one kernel-Hermes LOG_BATCH message she writes on her own turn,
the source being the sender the kernel stamped.  Records that cannot go yet
are counted and reported with the next flush.  LOG-SHOW (Hera only) reads
the ring back -- it had no reader.

Found by the first test that filled it: ring growth overwrote the oldest
record and put blank slots inside the live range.  Fixed test first.

Three ISAs: POST 1052 passed; new parity baseline word_count=526
hash=0x82f4ae7cb2e2d424 (deliberate).  CLAUDE.md: Phase 8 PKI closed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

kernel/Makefile

@@ -592,7 +592,8 @@ LOADER_EXTRA_SRCS := \
     $(KERNEL_SRC)/vm/stadium_words.c \
     $(KERNEL_SRC)/vm/stadium_blocks.c \
     $(KERNEL_SRC)/vm/session.c \
-    $(KERNEL_SRC)/vm/kernel_hermes.c
+    $(KERNEL_SRC)/vm/kernel_hermes.c \
+    $(KERNEL_SRC)/vm/vm_log_buffer.c
 
 KERNEL_EXTRA_SRCS := $(LOADER_EXTRA_SRCS)