revert(v4.0.0): step 6d, the wait, is backed out -- two reviews found it unsound

Ruled 2026-10-08.  The engine, the nucleus and their tests are as they
were at dfabfa46, before step 6d; the code of the wait and its tests are
in history at 075385ab..2cf37aab.  The limit of MESH.md 7b.7 stands: a
node that is stuck can hold up its neighbours until Hera kills it.

MESH.md 7c is kept as the record of the design as approved, and 7c.6 says
what was built, what the two reviews found, the cause the findings share
-- a node's message machinery runs on the stacks its text is using, and a
fault abandons whatever was in progress -- and what a second attempt
must settle before anything is built.

Kept from it, in hosted-check: a line that leaves 29 values on the stack,
and WORDS with 26 values on it.  Both hung the products at some commit of
the wait.

make -C v4 test and sanitize at both widths, hosted-check, lint; three
bare-metal boots typing both.  POST 538 of 538, word_count=317,
dict_hash=0xc0769523a47b7dc3 on all six: the hash of step 6c's code.

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

v4/tests/test_host_quit.c

@@ -63,7 +63,7 @@ static v4_heat       h;
 static v4_text       tx;
 static v4_cell       w_key, w_key_end, w_fault, capsule_latest;
 static v4_cell       w_idle;             /* (IDLE): where the node waits for a message */
-static v4_cell       w_idle_end;         /* (LINE): the word after it */
+static v4_cell       w_idle_end;         /* (PASS-ON): the word after it */
 static char          out[V4_CONSOLE_CAP + 1];
 
 /* STORAGE (MESH.md section 8).  The node asks its kernel for its blocks, and
@@ -213,7 +213,6 @@ static int run_line(long max)
     while (steps < max && idle < 64) {
         (void)v4_exec_step_word(&n, &es, &h);
         steps++;
-        (void)v4_node_offer_as_write(&n);                               /* in the wait: what it offers is a write, the kernel and the console taking at once */
         if (n.asking && n.ask_port == 0) { kernel_serve(); v4_node_port_served(&n); continue; }   /* a request */
         if (n.asking && n.ask_port == CONSOLE_PORT) {                   /* a word of a message from the node */
             v4_cell word = n.request;
@@ -871,7 +870,7 @@ int main(void)
     printf("  capsule: %ld words\n", (long)v4_text_here(&tx) - 16);
     if (failures) { printf("  %d checks, %d failures\n", checks, failures); return 1; }
     w_idle = v4_text_word(&tx, "(IDLE)");
-    w_idle_end = v4_text_word(&tx, "(LINE)");          /* the word after (IDLE) in quit.v4 */
+    w_idle_end = v4_text_word(&tx, "(PASS-ON)");       /* the word after (IDLE) in quit.v4 */
     w_key = v4_text_word(&tx, "KEY");
     w_key_end = v4_text_word(&tx, "CR");               /* the word after KEY in core.v4 */
     w_fault = v4_text_word(&tx, "(FAULTS)");
@@ -1134,21 +1133,6 @@ int main(void)
         }
         printf("  %u values may wait on the stack while the next line is typed and interpreted\n", most);
         CHECK(most + 4u >= V4_DATA_DEPTH, "the prompt and the interpreter take no more than four cells of the stack");
-        /* one more than may wait: the line ends in an error that says so, and the node goes on (found by the review of step 6d) */
-        {
-            char line[4 * V4_DATA_DEPTH + 16];
-            size_t at = 0;
-            unsigned m;
-            const char *r;
-            boot_bare();
-            for (m = 0; m < most + 1; m++) at += (size_t)snprintf(line + at, sizeof line - at, "1 ");
-            snprintf(line + at, sizeof line - at, "\n");
-            r = say(line);
-            CHECK(strstr(r, "Stack overflow") != NULL && strstr(r, " ERROR\nok> ") != NULL, "a line that leaves one value more than may wait ends in an error that says so: \"%s\"", r);
-            CHECK(strcmp(say("1 2 + .\n"), "3  ok\nok> ") == 0, "and the next line is done as usual");
-            for (m = 0; m < 2000 && !node_idle(); m++) (void)v4_exec_step_word(&n, &es, &h);   /* it finishes what it was doing when its answer went */
-            CHECK(n.mem[MQ_COUNT] == 0 && node_idle(), "with nothing left among the messages waiting, and the node at its ports");
-        }
     }
 
     /* ---- how much of the data stack a line has ---- */