feat(v4.0.0): the wait replaces looking and the console release; step 6d written up

The engine's console release (v4_fabric_interrupt_error), a device's
pending, and the count of words since a look are removed: nothing uses
them.  MESH.md 4.1, 7b and 7c say what was built, where it differs from
what was approved and why, and what is still a limit; step 6d is marked
built, with the defects found on the way.

make -C v4 test and sanitize at both widths, hosted-check, lint; three
bare-metal boots.  POST 538 of 538, word_count=317,
dict_hash=0x6a39c0bb9d183418 on all six.

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

v4/include/v4/fabric.h

@@ -26,7 +26,6 @@ typedef struct {
     int (*take)(void *self, v4_cell value);   /* the node wrote `value`: 1 if it is taken, 0 if not yet */
     int (*give)(void *self, v4_cell *value);  /* the node is reading: 1 with a word in *value, 0 if not yet */
     void *self;
-    int (*pending)(void *self);               /* 1 if it has a word to give that has not been asked for; may be 0: it never says */
 } v4_device;
 
 /* One end of a wire. */
@@ -56,7 +55,6 @@ typedef struct {
     v4_place *place;
     unsigned  capacity;
     v4_cell   gone_error;                /* see v4_fabric_gone_error; 0: none */
-    v4_cell   interrupt_error;           /* see v4_fabric_interrupt_error; 0: none */
 } v4_fabric;
 
 /* An empty fabric with room for `capacity` nodes, in `places`. */
@@ -73,19 +71,6 @@ void v4_fabric_init(v4_fabric *f, v4_place *places, unsigned capacity);
  * is how a fabric begins, nothing is raised. */
 void v4_fabric_gone_error(v4_fabric *f, v4_cell code);
 
-/* A NODE BLOCKED WRITING TO A NODE THAT DOES NOT READ.  Of two neighbours
- * one may write to the other without looking (docs/v4.0.0/MESH.md 7a), and
- * is then blocked until the other reads; if the other never does, it is
- * blocked for ever, and if it is the node the console is on, nothing can be
- * typed to it again.  So: when a node that can take an error is blocked
- * writing to another node, on the first word of a message (node.h,
- * v4_node_words_since_look: nothing of the message has gone), and a device
- * on one of its own ports says it has something pending for it, the error
- * `code` is raised on the node: it gives up that message and goes on, to
- * read what the device has.  Only a device with a `pending` function can
- * do this.  With `code` 0, which is how a fabric begins, it never happens. */
-void v4_fabric_interrupt_error(v4_fabric *f, v4_cell code);
-
 /* More room: `places`, of `capacity` no less than before, takes over; every
  * node keeps its number and its wiring. */
 void v4_fabric_grow(v4_fabric *f, v4_place *places, unsigned capacity);

v4/include/v4/image.h

@@ -65,11 +65,6 @@ typedef struct {
  * port". */
 #define V4_ERROR_NO_ONE 18
 
-/* The nucleus's error for a node let go of a message it was blocked on the
- * first word of, because its console has a line for it (fabric.h,
- * v4_fabric_interrupt_error): "Interrupted". */
-#define V4_ERROR_INTERRUPTED 21
-
 /* The description of the nucleus built from v4/capsule (the generated file
  * defines it). */
 extern const v4_image v4_capsule_image;

v4/include/v4/node.h

@@ -113,7 +113,6 @@ typedef struct {
     unsigned      last_from;         /* the port the last read from "any" took its word from */
     unsigned      writers;           /* bit k: the neighbour on port k is blocked writing to this node */
     unsigned      readers;           /* bit k: the neighbour on port k is blocked reading from this node */
-    unsigned      since_look;        /* words taken from this node since it last fetched either of those */
     unsigned      offers;            /* bit k: a word is offered on port k (the wait: docs/v4.0.0/MESH.md 7c) */
     v4_cell       offer[V4_PORTS];   /* the words offered */
     int           waiting;           /* non-zero: the read it is blocked in is the wait */
@@ -225,13 +224,6 @@ void v4_node_port_attach(v4_node *n, v4_cell base);
 /* The neighbour has taken what the node wrote. */
 void v4_node_port_served(v4_node *n);
 
-/* How many words the node has had taken since it last looked at its
- * neighbours (a fetch of either of the two status addresses).  A node that
- * looks before it begins a message (MESH.md 7a) and is blocked writing with
- * this at 0 is blocked on the first word of the message: nothing of it has
- * gone. */
-unsigned v4_node_words_since_look(const v4_node *n);
-
 /* THERE IS NO ONE ON THE PORT the node is blocked at -- writing to it, or
  * reading from that one port -- and there will not be.  A node that can
  * take an error (it has an error register and a fault table: node.h,