feat(v4.0.0): messages are whole and wait on the wire -- a node keeps none but the one it is doing

Step 6e, tasks 2 and 3 (docs/v4.0.0/MESH.md 7d).  The nucleus puts, looks
at, takes, moves and drops whole messages through the six addresses after
its ports; its own ring of messages waiting, the refusals owed, (GATE) and
the looking words' use are gone.  SEND, an answer, a NACK and a GONE go or
are refused at once; what a text prints waits for room; a text is not
begun until the wire its answer goes by has room for it, and that room is
kept.  The lone node's host (v4/system/boot.c) keeps its two wires and
does its operations; the test hosts' consoles put and take whole messages
through the fabric.  New: tests/test_host_depth.c, every message path of
a mesh node at every depth of both stacks.

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

v4/tools/depthsweep.py

@@ -65,6 +65,8 @@ for k in [0, 1, shallow] + list(range(ddepth - 10, ddepth + 3)):
     check('SEND with no way', k, [': SD S" 1 DROP" 5 SEND ;'] + v + ['SD', '77 .'], 'Argument out of range' if sh else None)
     check('a write to an empty port', k, v + ['5 7 PORT!', '77 .'], 'No one on that port' if sh else None)
     check('an unknown word', k, v + ['NOSUCHWORD', '77 .'], 'UNKNOWN WORD' if sh else None)
+    check('a loop that prints 400 numbers', k, [': PR 400 0 DO I . LOOP ;'] + v + ['PR', '77 .'], ' 398 399  ok' if sh else None)
+    check('SEND by a way with no one on the port', k, ['5 7 ROUTE', ': SP S" 1 DROP" 5 SEND ;'] + v + ['SP', '77 .'], 'No one on that port' if sh else None)
 
 def nest(n, inner):
     return [': N1 %s ;' % inner] + [': N%d N%d ;' % (i, i - 1) for i in range(2, n + 1)] + ['N%d' % n]
@@ -76,6 +78,8 @@ for n in [1, rshallow] + list(range(rdepth - 12, rdepth + 3)):
     check('WORDS, calls deep', n, nest(n, 'WORDS') + ['77 .'], '77  ok')
     check('a line typed during AWAIT, calls deep', n, nest(n, '5 AWAIT') + ['77 .', '88 .'], '77  ok')
     check('SEND with no way, calls deep', n, nest(n, 'S" 1 DROP" 5 SEND') + ['77 .'], '77  ok')
+    check('a loop that prints 400 numbers, calls deep', n, nest(n, '400 0 DO I . LOOP') + ['77 .'], '77  ok')
+    check('SEND by a way with no one on the port, calls deep', n, ['5 7 ROUTE'] + nest(n, 'S" 1 DROP" 5 SEND') + ['77 .'], '77  ok')
 
 with ThreadPoolExecutor(max_workers=8) as pool:
     found = [f for f in pool.map(judge, cases) if f]