feat(v4): the system hands no GONE on; (GONE-HOOK) goes (MESH step 7, increment 2)

Ruling 7 as amended: the kernel tells a node's going, so the system's
hand-on is not used.  (GONE-HOOK), (DOWN) and (RUN) go from quit.f18, and
COLD's hook-clearing from system.f18; the cell is free again.  The tests of
the hand-on go with it (mesh: the hand-on checks and the fourth disturbed
exchange; depth sweep: path 10, as before 529ba0fc).  A believed GONE going
no further is still checked.  test_host_unit.c's message for GONE down the
graph now says the kernel tells.  MESH.md: 9a.6 items 5 and 7, and step 7's
record of both increments.

Suite EXIT 0; depth sweep 230 runs, 0 failures; mkcapsule lint 0
violations.  Hosted and bare metal, all three ISAs: word_count=317
dict_hash=0xfec8c47cfc6f437f.

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

v4/tests/host_map.h

@@ -119,7 +119,7 @@
 /* THE IMAGE RECORD: where the system's source says, with `store`, the addresses a host needs (v4/image.h): where the
  * node waits for a message, its fault table, and KEY's code. */
 #define ROM_IMG      (BUF0_W - 119)             /* idle, fault table, KEY, the word after KEY: 4 cells */
-/* FREE, plain memory: BUF0_W - 22; - 115 .. - 113; BUF0_W - 144 .. - 141 (what a flush makes zero after
+/* FREE, plain memory: BUF0_W - 22 .. - 21; - 115 .. - 113; BUF0_W - 144 .. - 141 (what a flush makes zero after
  * a full output buffer); and OUT_W - 144 .. OUT_W - 65.  They and
  * the cells above held the messages waiting, the refusals owed and what went with them (MESH.md 7a, 7b), which a
  * node no longer keeps. */
@@ -205,7 +205,6 @@ enum { V4_ROM_ERRORS(ROM_ERR_ENUM_) ROM_ERR_END_ };
 #define ROM_ADDR_TOP      ((v4_cell)(V4_NODE_WORDS + V4_ROM_WORDS - 1u))   /* the top of the address space */
 #define WORD_DEFINED   (BUF0_W - 11)             /* the xt of the word that is told of each new entry, or 0 */
 #define WORD_FORGOTTEN (BUF0_W - 12)             /* the xt of the word that is told when entries go, or 0 */
-#define GONE_HOOK      (BUF0_W - 21)             /* the xt of the word a believed GONE is handed to, or 0 (MESH.md 9a.2, ruling 7) */
 #define LOG_LEVEL    (BUF0_W - 5)               /* the level at or below which a message is printed */
 #define BOOT_CELLS   (BVARS + 14)               /* (BOOT): DP and LATEST as the loader left them, 2 cells */
 #define BUF0_W       (BVARS - (v4_cell)(V4_BLOCK_SLOTS * V4_BLOCK_CELLS))   /* the block window: the kernel's slots, 256 cells each (v4/blocks.h) */
@@ -331,7 +330,6 @@ static unsigned host_branch_slots(void)
     X("(OUT)", OUT_W) \
     X("(WORD-DEFINED)", WORD_DEFINED) \
     X("(WORD-FORGOTTEN)", WORD_FORGOTTEN) \
-    X("(GONE-HOOK)", GONE_HOOK) \
     X("BLOCK#", V4_REQ_BLOCK)               /* the kernel's block requests (v4/blocks.h) */ \
     X("BUFFER#", V4_REQ_BUFFER) \
     X("UPDATE#", V4_REQ_UPDATE) \