fix(v4.0.0): wire review round 1 -- tests for the wake-up order and for waking only on enough room; no overflow moving a message; sleep for impossible room answers at once

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

v4/include/v4/fabric.h

@@ -148,7 +148,7 @@ void v4_fabric_wake(v4_fabric *f, unsigned id);
  * Sleep (8) and sleep for room (9) are the two that wait: the node stays
  * blocked, executing nothing, until a message has come to one of its wires
  * since it last fetched which wires have one -- or, for 9, until its wire
- * has the room.  A message has "come" when a put or a move or a device put
+ * has the room (a wire that can never have the room answers 1 at once).  A message has "come" when a put or a move or a device put
  * put it on the back of a queue; fetching Have clears that for all of the
  * node's wires.
  *

v4/include/v4/wire.h

@@ -30,6 +30,9 @@
 
 #define V4_WIRE_HEADER 7u                /* the words of a message that are not its text */
 
+/* a wire must be able to hold the largest message there is: 1,024 characters */
+typedef char v4_wire_holds_a_message[(V4_WIRE_CELLS >= 7 + 1024 / 4) ? 1 : -1];
+
 typedef struct {
     v4_cell  cell[V4_WIRE_CELLS];   /* the messages, one after another, going round */
     unsigned head;                  /* where the front message begins */