fix(v4.0.0): step 6e review round 2 -- only the message looked at is taken, moved or dropped; the kernel's port has no queue in a fabric; an answer nobody awaits is not a loss

- Engine: a wire keeps whether the message at its mark is the one last
  looked at; a node's take, move and drop of any other answer 3 and write
  nothing (MESH.md 7d.3).  A wire cut and made again between a look and a
  take no longer has a NACK done as text, or 256 cells written where one
  was looked for.
- Engine: v4_fabric_wire_kernel wires a kernel to a port with no queues;
  a message for it is refused at once, error 18, on a mesh as on the
  products.
- The result of a drop is looked at; a take that does not take has the
  message dropped, or gone past: nothing goes round.
- An answer nobody waits for is let go uncounted; (LOST) counts what should
  have been delivered or acted on and was not.  The flood's account is
  exact.
- Error 18 from under a word that was printing empties the data stack, as
  a fault does: that word's own values are not left there.
- Tests: the take and drop windows cut at every step, with and without
  another message put; a refusal owed to a stuck node whose wire is full.

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

v4/capsule/core.v4

@@ -229,8 +229,11 @@ header CMOVE
 \ wire would be; or, if it is about the node this one is waiting on,
 \ (A-SELF) is set for AWAIT to find (quit.v4).
 \ (WIRE) is not what it was afterwards: the NACK went by another.
+\ If the drop does not drop -- the wire was cut after the message was looked
+\ at, which let it go already -- nothing is counted and no one is told.
 : (REFUSE)
-  4 (DO) drop
+  4 (DO)  if DROPPED  drop ;                                 \ it was not there to drop -- its wire has been cut: nothing is counted or told
+  DROPPED: drop
   (LOST) a! @  1 +  !
   (IN)+2 a! @  -4 + if NOT  -1 + if NOT  2 + if ANSWER
   drop  (IN) a! @ (ONE) a! !  (IN)+1 a! @  jump TELL        \ about whom it was for; to its sender
@@ -350,6 +353,17 @@ header CMOVE
 \ ( -- )   go past the message (MINE) found: it stays on its wire
 : (SKIP)   (S-WIRE) a! @ (WIRE!)  7 (DO) drop ;
 
+\ ( -- )   A TAKE DID NOT TAKE the message (MINE) found.  The fabric takes
+\ only the message last looked at (MESH.md 7d.3), so either the wire has
+\ been cut -- and there is nothing there, or another message that has not
+\ been looked at -- or the message cannot be taken at all.  It is dropped,
+\ and counted in (LOST); if it cannot be dropped either it is gone past.
+\ Either way whoever goes through the messages next is at another one:
+\ nothing goes round on one that will not be taken.
+: (UNTAKEN)
+  (S-WIRE) a! @ (WIRE!)  4 (DO)  if GONE  drop  jump (SKIP)
+  GONE: drop  (LOST) a! @  1 +  ! ;
+
 \ ( -- how )   take the message (MINE) found, which has one word of text:
 \ its seven words stay in (IN), and its word goes to (ONE).  0: it is
 \ taken.  Anything else: it is not -- the wire was cut after the message
@@ -388,7 +402,11 @@ header CMOVE
 \ The three cells and two return entries this needs are tried first.
 \ WITH NO ONE ON THE PORT -- when it waits for room, or when it comes to
 \ put -- what was printed cannot be sent.  While the text is being done
-\ that is its error, 18.  Once it has been finished with, what it printed
+\ that is its error, 18; and the data stack is emptied first, as a fault
+\ empties it.  A word that raises an error has taken its own arguments
+\ off; this one comes from under whatever word was printing, in the
+\ middle of its work, and what that word had on the stack is nothing its
+\ caller can use (as first built those values were left there).  Once it has been finished with, what it printed
 \ is let go and counted in (LOST), and the text is said to have ended in
 \ an error: (LINE-STATUS), which is the word then sent of how it ended.
 : (FLUSH-OUT)
@@ -401,7 +419,7 @@ header CMOVE
   (WAIT-ROOM) if ROOM
   NOONE: drop  (QUIET) a! @ if TELL
   drop  (OUT) (OUT^) a! !  (LOST) a! @  1 +  !  2 (LINE-STATUS) a! ! ;
-  TELL: drop  NODE-ERROR b! 18 !b ;
+  TELL: drop  DSTACK-DEPTH b! a !b  NODE-ERROR b! 18 !b ;          \ the data stack is emptied, as by a fault: see below
   ROOM: drop
   (PRINT-TO) a! @  2 (HDR)
   (OUT^) a! @ a!  0 !+  0 !+  0 !