feat(v4.0.0): word-level access control at the prompt, as v3

- Each entry's flags cell also holds v3's four fields: denied, pinned,
  mode and a 16-bit TTL.
- compile.v4: INTERPRET checks every word it is about to execute or
  compile -- recheck at TTL 0, else count down; a denied word is refused
  with v3's line, the stack emptied and the line ended.
- capsule/acl.v4: ACL-MODE@ ACL-MODE! ACL-TTL@ ACL-TTL! ACL-ALLOW@
  ACL-ALLOW! ACL-PINNED? ACL-PIN ACL-INHERIT ACL-INIT-PRIMITIVES ACL-HEAT@
  ACL-WORD-ID, and ACL-HOOK.
- capsule/ACL.fth: v3's ACL.4th as FORTH source the node compiles; loading
  it switches access control on.
- v3 checks every execution, inside definitions too.  v4's code is native,
  so it checks a word when it is compiled as well as when interpreted; a
  call compiled while the word was allowed is not checked again.
  DECOMPOSITION.md 5.20 says so.
- ACL-HEAT@ is 0 until heat is readable (D-6).
- tests/test_host_quit.c: seven transcripts of the v3 binary; the policy
  file loaded and exercised; COLD.

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

v4/tests/host_map.h

@@ -64,6 +64,7 @@
 #define SRC          (BVARS + 8)
 #define SRC_HOOK     (BVARS + 9)
 #define STORAGE_REG  (BVARS + 10)
+#define ACL_HOOK     (BUF0_W - 6)               /* the xt of the access control recheck word, or 0 */
 #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 - 2 * 256)          /* the two block buffers, 256 cells each */
@@ -132,6 +133,7 @@ static int host_load(v4_text *tx, v4_node *n, const char *const *files, unsigned
     v4_text_constant(tx, "(B)", BVARS);
     v4_text_constant(tx, "(BOOT)", BOOT_CELLS);
     v4_text_constant(tx, "(LOG-LEVEL)", LOG_LEVEL);
+    v4_text_constant(tx, "(ACL-HOOK)", ACL_HOOK);
     v4_text_constant(tx, "SCR", SCR);
     v4_text_constant(tx, "BLK", BLK);
     v4_text_constant(tx, "(SRC)", SRC);