feat(v4.0.0): POST is the kernel's -- the boot feeds the cases, and nothing of the harness is on the node

The boot runs POST with the runner (v4/system/post.c) after the capsules:
it feeds the 538 cases to the node and judges them from outside.  A
case's printing no longer reaches the console.  What the cases define
stays in the dictionary, as in v3; the system is sealed after POST and
the boot prints PARITY:V4_SYSTEM word_count=N dict_hash=..., as v3 prints
its parity after POST.

Gone: capsules/v4/post79.4th and its blocks 7000 up; the harness words;
(CATCH) and (EMIT-HOOK), with what EMIT and the prompt loop did for them.

The generator runs v3 on the lines as the kernel sends them, without the
capsule's "T| ".  One expected result follows from that: >IN.initial
prints 6, not 9.

make -C v4 test, sanitize and hosted-check pass; amd64, aarch64 and
riscv64 boot, POST 538 of 538, word_count=411, dict_hash
0x6fb1d09418b189ee on all six: logs/20261007-105118, -105335, -105651.
T{ is unknown at the prompt; RS1 prints 42 42 before and after COLD.  A
scratch build with one expectation changed names the case and ends
PARITY:FAIL, POST: FAILED.

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

v4/Makefile

@@ -139,7 +139,7 @@ CAPSULE_DIR_C := $(BINDIR)/capsule_generated.c
 
 # the kernel's capsule code: find, check the hash, verify the signature,
 # split a payload into blocks
-SYSTEM_SRCS   := $(HERE)/system/boot.c \
+SYSTEM_SRCS   := $(HERE)/system/boot.c $(HERE)/system/post.c $(HERE)/system/post_cases.c \
                  $(addprefix $(ROOT)/kernel/src/capsule/,capsule_find.c capsule_validate.c capsule_sig.c capsule_blocks.c) \
                  $(ROOT)/kernel/src/hash/xxhash64.c $(ROOT)/kernel/src/crypto/x509_ed25519.c $(CRYPTO_SRCS)
 # The kernel's sources are held to the kernel's warnings, not this model's.
@@ -169,7 +169,7 @@ $(foreach i,$(HOSTED_ISAS),$(eval $(call HOSTED_RULE,$(i))))
 
 # `make post` boots the amd64 system alone, which is the quick check after a
 # change to the vocabulary: nucleus, forth79.4th, POST, prompt.  `make
-# post79` writes the POST capsule, ../capsules/v4/post79.4th, again from
+# post79` writes POST's cases, system/post_cases.c, again from
 # v3's cases and tools/post79_rules.py (tools/mkpost.py); it needs the
 # hosted v3 binary.
 .PHONY: post post79