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/tests/test_host_unit.c

@@ -31,6 +31,7 @@
 #include "v4/manage.h"
 #include "v4/blocks.h"
 #include "v4/message.h"
+#include "v4/post.h"
 #include "v4/text.h"
 #include "block_subsystem.h"
 #include <stdio.h>
@@ -154,7 +155,6 @@ static int host_open(void *self, const char *name, unsigned len)
     (void)self;
     if (len == 17 && memcmp(name, "v4:nucleus-64.f18", 17) == 0) { hera_reads.is_f18 = 1; hera_reads.cells_at = 0; return 1; }
     if (len == 14 && memcmp(name, "v4:forth79.4th", 14) == 0) return read_file(&hera_reads, "forth79.4th");
-    if (len == 13 && memcmp(name, "v4:post79.4th", 13) == 0) return read_file(&hera_reads, "post79.4th");
     return 0;
 }
 static int host_cell(void *self, v4_cell *w)
@@ -277,6 +277,30 @@ static const char *tell(v4_cell node, const char *text)
 }
 static int told(v4_cell node, const char *text) { return tell(node, text)[0] == 0 && ended == 1 && ended_how == V4_TEXT_COMPLETED; }
 
+/* POST's host, for the node numbered 10 (v4/include/v4/post.h): a line is
+ * told to it from the console, and what it prints is handed to the runner. */
+static int post_line(void *self, const char *text, unsigned text_len, char *out, unsigned cap, unsigned *len)
+{
+    static char line[V4_MSG_MAX_CHARS + 1];
+    const char *r;
+    (void)self;
+    *len = 0;
+    if (text_len > V4_MSG_MAX_CHARS) return -1;
+    memcpy(line, text, text_len); line[text_len] = 0;
+    r = tell(10, line);
+    if (ended != 1 || ended_from != 10) return -1;
+    *len = printed_len;
+    memcpy(out, r, printed_len < cap ? printed_len : cap);
+    return (int)ended_how;
+}
+static char     post_said[2048];
+static unsigned post_said_len;
+static void post_say(void *self, const char *text, unsigned len)
+{
+    (void)self;
+    if (post_said_len + len < sizeof post_said) { memcpy(post_said + post_said_len, text, len); post_said_len += len; post_said[post_said_len] = 0; }
+}
+
 /* Every line of a capsule of FORTH blocks, told to a node from the console:
  * how many lines did not complete. */
 static unsigned load(v4_cell node, const char *file)
@@ -376,7 +400,16 @@ int main(void)
     }
     CHECK(strcmp(tell(10, "NODE-ME ."), "0 ") == 0 && refused == 0, "it asks where it is, and is answered");
     CHECK(load(10, "forth79.4th") == 0, "it takes in FORTH-79");
-    CHECK(load(10, "post79.4th") == 0 && post_passed[10] == 1 && post_other == 0, "and passes POST");
+    {
+        v4_post_host host;
+        v4_post_tally tally;
+        host.self = 0; host.n = node_numbered(10); host.line = post_line; host.say = post_say;
+        CHECK(v4_post_run(&host, v4_post_cases, v4_post_case_count, &tally) && tally.tests == 538 && tally.pass == 538 && tally.fail == 0
+              && strstr(post_said, "PARITY:V4_POST tests=538 pass=538 fail=0\n") != NULL && strstr(post_said, "POST FAIL") == NULL,
+              "and passes POST, which the kernel runs on her: %u of %u, %u failed; \"%s\"", tally.pass, tally.tests, tally.fail, post_said);
+    }
+    CHECK(strstr(tell(10, "T{"), "UNKNOWN WORD") != NULL, "nothing of POST's harness is on her: \"%s\"", printed);
+    CHECK(strcmp(tell(10, "RS1"), "42 42 \n") == 0, "what POST's cases defined is: \"%s\"", printed);
     CHECK(load(10, "hera.4th") == 0, "and its own capsule, which makes it Hera");
     CHECK(told(10, "(SEAL)"), "that is the system it comes back to");
 
@@ -387,9 +420,10 @@ int main(void)
         CHECK(ended == 1 && ended_how == V4_TEXT_COMPLETED && ended_from == 10, "Hera births four nodes and joins them: \"%s\"", r);
     }
     CHECK(born_count == 4 && refused == 0, "four nodes were asked for: %u", born_count);
-    CHECK(post_passed[10] == 1 && post_passed[11] == 0 && post_passed[12] == 0 && post_passed[13] == 0 && post_passed[14] == 0 && post_other == 0,
-          "a node she births is not POSTed: POST is the kernel's, once, on Hera: %u; %u %u %u %u, %u failed",
+    CHECK(post_passed[10] == 0 && post_passed[11] == 0 && post_passed[12] == 0 && post_passed[13] == 0 && post_passed[14] == 0 && post_other == 0,
+          "a node she births is not POSTed, and no node prints a POST tally: POST is the kernel's, once, on Hera: %u %u %u %u %u, %u failed",
           post_passed[10], post_passed[11], post_passed[12], post_passed[13], post_passed[14], post_other);
+    CHECK(strstr(tell(10, "COLD"), "Cold Start") != NULL && strcmp(tell(10, "RS1"), "42 42 \n") == 0, "COLD on Hera comes back to a system that has what POST's cases defined: \"%s\"", printed);
     CHECK(parity_count == 4 && parity_number[0] == 11 && parity_number[1] == 12 && parity_number[2] == 13 && parity_number[3] == 14, "the parity of each was recorded: %u", parity_count);
     CHECK(parity_hash[0] == parity_hash[1] && parity_hash[1] == parity_hash[2] && parity_hash[2] == parity_hash[3],
           "and their dictionary hashes are the same: %016llx %016llx %016llx %016llx",