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/fabric.c

@@ -157,6 +157,15 @@ int v4_fabric_wire(v4_fabric *f, unsigned a, unsigned pa, unsigned b, unsigned p
     return 1;
 }
 
+int v4_fabric_wire_kernel(v4_fabric *f, unsigned a, unsigned pa, const v4_device *device)
+{
+    if (!there(f, a, pa) || !device) return 0;
+    cut(f, a, pa);
+    f->place[a].wire[pa].kind = V4_WIRE_DEVICE;
+    f->place[a].wire[pa].device = device;      /* and no queues: it takes no messages */
+    return 1;
+}
+
 int v4_fabric_wire_device(v4_fabric *f, unsigned a, unsigned pa, const v4_device *device)
 {
     if (!there(f, a, pa) || !device) return 0;
@@ -346,7 +355,7 @@ static int operate(v4_fabric *f, unsigned id, v4_cell *how)
         break;
     case 2:                                                  /* take */
         if (!rx) { *how = V4_WIRE_NO_ONE; break; }
-        if (rx->mark >= rx->used) { *how = V4_WIRE_NO_MESSAGE; break; }
+        if (rx->mark >= rx->used || !rx->looked) { *how = V4_WIRE_NO_MESSAGE; break; }   /* only the message last looked at (wire.h) */
         (void)v4_wire_look(rx, h);
         cells = v4_wire_cells(h[6]) - V4_WIRE_HEADER;
         if (!span_ok(n, a, V4_WIRE_HEADER) || !span_ok(n, b, cells)) { *how = V4_WIRE_NOT_A_MESSAGE; break; }
@@ -354,12 +363,12 @@ static int operate(v4_fabric *f, unsigned id, v4_cell *how)
         break;
     case 3:                                                  /* move */
         if (!rx) { *how = V4_WIRE_NO_ONE; break; }
-        if (rx->mark >= rx->used) { *how = V4_WIRE_NO_MESSAGE; break; }
+        if (rx->mark >= rx->used || !rx->looked) { *how = V4_WIRE_NO_MESSAGE; break; }
         to = a >= 0 && a < (v4_cell)V4_PORTS ? going(f, id, (unsigned)a) : 0;
         *how = to ? v4_wire_move(rx, to) : V4_WIRE_NO_ONE;
         break;
     case 4:                                                  /* drop */
-        *how = rx ? v4_wire_drop(rx) : V4_WIRE_NO_ONE;
+        *how = !rx ? V4_WIRE_NO_ONE : rx->looked ? v4_wire_drop(rx) : V4_WIRE_NO_MESSAGE;
         break;
     case 5:                                                  /* put */
         if (!tx) { *how = V4_WIRE_NO_ONE; break; }

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)