feat(v4.0.0): refusals and waits on bare metal, and step 6c written up

The bare-metal host hands a waiting node the next line typed, as the
hosted one does: 5 AWAIT, then 7 8 * . -- Interrupted, then 56.

amd64, aarch64 and riscv64 boot, POST 538 of 538, word_count=317,
dict_hash 0x54520ade672566ad, the same as the three hosted programs:
logs/20261007-202737, -203230, -203616.

MESH.md step 6c: what was built, how it was verified, and two things
found on the way that are not mended and are for ruling: Hera blocked
writing to a stuck node, and a message that can go round for ever between
two nodes whose ways disagree.

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

v4/README.md

@@ -133,6 +133,14 @@ The two products are not yet this: they become the five nodes at steps 8
 and 9.
 A node she births is not POSTed: POST is the kernel's, once, on Hera.
 
+**Refusals and waits** (`MESH.md` 7b, step 6c). No message is lost without
+its sender being told, and no node waits for ever. A node with no room for
+a message, or no way to pass it on, sends its sender a NACK; `(REFUSED)`
+counts them. `AWAIT` ends in an error if the answer is not going to come:
+"Message refused", "Node gone", or "Interrupted" when a line is typed at
+the console. `n KILL` on Hera removes node n and tells every other node it
+is gone.
+
 **Blocks** (`MESH.md` step 6). The block words are the kernel's, as they
 are for a v3 VM: `BLOCK`, `BUFFER`, `UPDATE`, `SAVE-BUFFERS` and
 `EMPTY-BUFFERS` each write one request to port 0, by block number only