feat(v4): the ROM's slot packer, word for word with asm.c

(OP) (LIT) (BRANCH) (BRANCH>) (RESOLVE) (LABEL), entries 6-11: the code
generator of any language built on the machine (MACHINE.md 2.1).  asm.c's
layout rules with text.c's branch placement; 400 random sequences agree
word for word with asm.c at both widths, memory-full and out-of-reach are
refused on both sides, and a ref with no branch is refused, not looped on.

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

capsules/v4/rom/main.f18

@@ -13,3 +13,9 @@
   jump (FIND)                   \ 3   ( -- rec | 0 )
   jump (DEFINE)                 \ 4   ( value kind -- )
   jump (OPCODE)                 \ 5   ( -- op | -1 )
+  jump (OP)                     \ 6   ( op -- )
+  jump (LIT)                    \ 7   ( v -- )
+  jump (BRANCH)                 \ 8   ( op target -- )
+  jump (BRANCH>)                \ 9   ( op -- ref )
+  jump (RESOLVE)                \ 10  ( ref target -- )
+  jump (LABEL)                  \ 11  ( -- addr )