feat(v4.0.0): every message begins through the wait -- a stuck node holds up no one

(GATE) offers a message's first word and sleeps until it is taken, taking
in whatever is written to the node meanwhile; (PAY) offers every refusal
owed at once, one to a port; a node that owes one sleeps in the wait.
Writing without looking, looking again and again, and the lower-number
rule are gone.  Text from the console for a node whose own text waits to
begin a message ends that text Interrupted.  The lone node's hosts serve
an offer as a write.  MESH.md 7c; plan step 6d task 2.

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

v4/system/boot.c

@@ -107,6 +107,7 @@ static int run_line(const v4_boot *b, const char *text, unsigned len, char *keep
     for (;;) {
         (void)v4_exec_step_word(n, b->es, b->h);
         if (n->stopped) return V4_BOOT_LINE_STOPPED;
+        (void)v4_node_offer_as_write(n);                       /* in the wait (MESH.md 7c): what it offers is a write, here where whatever is on a port takes at once */
 
         if (n->asking && n->ask_port == KERNEL_PORT) {         /* a request: the kernel's turn */
             if (v4_blocks_serve(&boot_blocks, n, n->request)) {       /* a block, as for any node */