feat(v4.0.0): every node asks the kernel for its blocks; a born node is not POSTed

A block is a kernel request, as ENGINE.md 3.3 has it: the node puts the
block's number and the address of 256 cells on its stack and writes the
request to port 0, and the kernel leaves the status there.  The requests
are -1, read, and -2, write, the same for every node.  v4/system/blocks.c
serves them from the kernel's block subsystem, which is v3's.  The four
storage registers are gone from the engine.

The device that spoke block messages (4a505a15) is withdrawn with its
test and its message types: Captain Bob ruled on 2026-10-07 that it, a
node's own drive, and nodes with no storage had left the OS as designed
(docs/v4.0.0/MESH.md 8.5).

Hera no longer sends POST to the nodes she births: POST is the kernel's,
once.  Every node has its kernel on port 0; it serves a node's blocks and,
for Hera alone, her requests for nodes and capsules.

Bare metal: the node boots and is POSTed against POST's own block RAM,
and the kernel's chain -- fast RAM, the ramdrive, the virtio disk -- is
set up after POST and before the prompt, as on the v3 path.  The disk is
read and not written: nothing in v4 yet gives the owner's word that it
may be formatted.  A hosted program has the chain's fast RAM, as hosted
v3 has with no disk.  Error 17 is Storage refused.

make -C v4 test and sanitize pass at both widths; hosted-check passes on
three ISAs; amd64, aarch64 and riscv64 boot, POST 538 of 538, with the
typed session: logs/20261007-081603, -081839, -082226.  The hashes are
the same on all six.

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

v4/include/v4/node.h

@@ -116,10 +116,6 @@ typedef struct {
     v4_cell       dstack_reg;        /* its word address, or -1 */
     v4_cell       rstack_reg;        /* its word address, or -1 */
 
-    /* The block storage device (D-19).  See v4_node_storage_attach. */
-    v4_cell        storage_reg;      /* word address of its four registers, or -1 */
-    unsigned char *storage;          /* the blocks, 1024 bytes each */
-    unsigned       storage_blocks;   /* how many */
 
     /* NODE-ERROR as a trap (D-18).  See v4_node_error_attach. */
     v4_cell       error_reg;         /* its word address, or -1 */
@@ -335,31 +331,14 @@ void v4_node_fault(v4_node *n, unsigned kind, v4_cell addr);
  * detaches both (-1); the addresses are the caller's choice (D-4). */
 void v4_node_stack_regs_attach(v4_node *n, v4_cell d, v4_cell r);
 
-/* THE BLOCK STORAGE DEVICE (DECOMPOSITION.md D-19, 5.11).
- *
- * Mass storage is a device service; until the mesh exists the model stands
- * in for it on the host node with four memory-mapped registers at `reg`:
- *
- *   reg + 0   BLOCK-NUMBER    which block, 0 .. blocks - 1
- *   reg + 1   BLOCK-ADDRESS   word address of 256 cells of node memory
- *   reg + 2   BLOCK-COMMAND   a store of 1 reads the block into those cells,
- *                             a store of 2 writes it from them
- *   reg + 3   BLOCK-STATUS    0 after a command that worked, -1 after one
- *                             that did not: no such block, cells that are
- *                             not all in memory, or an unknown command
- *
- * The first, second and fourth are memory words the device reads and writes;
- * only a store to the third does anything.  A block is 1024 bytes, and a
- * byte address is four times a word address plus 0 .. 3 (D-1), so a block
- * is 256 cells, four bytes to a cell, the first byte lowest, whatever the
- * cell width: a read leaves the rest of each cell zero, and a write takes
- * the low 32 bits.
- *
- * `bytes` is the caller's: `blocks` * 1024 bytes, which the device reads and
- * writes and never frees.  v4_node_reset detaches it (reg -1). */
+/* A BLOCK (DECOMPOSITION.md D-19, 5.11).  Mass storage is a device on a
+ * port that speaks messages (docs/v4.0.0/MESH.md section 8; storage.h); the
+ * node has nothing of it but these.  A block is 1024 bytes, and a byte
+ * address is four times a word address plus 0 .. 3 (D-1), so a block is 256
+ * cells, four bytes to a cell, the first byte lowest, whatever the cell
+ * width. */
 #define V4_BLOCK_BYTES 1024u
 #define V4_BLOCK_CELLS 256u
-void v4_node_storage_attach(v4_node *n, v4_cell reg, unsigned char *bytes, unsigned blocks);
 
 /* NODE-ERROR as a trap (DECOMPOSITION.md D-18, ruled 2026-10-04: every error
  * is guarded, shown, and returns the node to its prompt).