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/src/wire.c

@@ -14,6 +14,7 @@ void v4_wire_reset(v4_wire_queue *q)
     q->mark = 0;
     q->arrived = 0;
     q->freed = 0;
+    q->looked = 0;
 }
 
 unsigned v4_wire_cells(v4_cell length)
@@ -62,21 +63,24 @@ int v4_wire_put(v4_wire_queue *q, const v4_cell *header7, const v4_cell *text)
 
 void v4_wire_first(v4_wire_queue *q)
 {
+    q->looked = 0;
     q->mark = 0;
 }
 
 int v4_wire_next(v4_wire_queue *q)
 {
+    q->looked = 0;
     if (q->mark >= q->used) return V4_WIRE_NO_MESSAGE;
     q->mark += size_at(q, q->mark);
     return q->mark < q->used ? V4_WIRE_DONE : V4_WIRE_NO_MESSAGE;
 }
 
-int v4_wire_look(const v4_wire_queue *q, v4_cell *header7)
+int v4_wire_look(v4_wire_queue *q, v4_cell *header7)
 {
     unsigned i;
     if (q->mark >= q->used) return V4_WIRE_NO_MESSAGE;
     for (i = 0; i < V4_WIRE_HEADER; i++) header7[i] = q->cell[slot(q, q->mark + i)];
+    q->looked = 1;
     return V4_WIRE_DONE;
 }
 
@@ -91,6 +95,7 @@ static void remove_marked(v4_wire_queue *q)
     }
     q->used -= n;
     q->freed = 1;
+    q->looked = 0;
 }
 
 int v4_wire_take(v4_wire_queue *q, v4_cell *header7, v4_cell *text, unsigned text_cap)