feat(v4): the ROM assembles text as text.c does -- words, labels, macros, FOR, directives, start

word.f18: (NEXT-TOKEN) reads the console or a macro being expanded; labels,
branches by name (a label of the word, or a word, now or later), the
table of branches waiting, end of word, FOR/NEXT/UNEXT, macros, &NAME,
CONST+N, and (ONE), which dispatches a token.  A forward branch to a name
not yet defined waits on a placeholder symbol, filled in by (DEFINE).
dir.f18: constant set here #, ", store, and start, which resolves, clears
the tables the ROM used and runs the word it names.  main.f18: the ROM
itself, entry 12; on an error it stops at (ROM-FAILED) with the code and
line in its state, for the loader to report.  sym.f18 generalized: any
counted string, placeholders, a hash of only a name's own cells.

test_host_rom_asm.c gives test_text.c's own texts (accepted and refused),
its four real definitions and the ROM's directives to text.c and to the
ROM: the same words, the same errors on the same lines, at both widths.
The ROM is 2036 words.

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

capsules/v4/rom/main.f18

@@ -19,3 +19,29 @@
   jump (BRANCH>)                \ 9   ( op -- ref )
   jump (RESOLVE)                \ 10  ( ref target -- )
   jump (LABEL)                  \ 11  ( -- addr )
+  jump (ROM)                    \ 12  the ROM itself: where the machine starts
+
+\ ( -- )   the state the ROM begins from: code goes to ORIGIN, nothing read,
+\ nothing defined
+: (INIT)
+  (CLEAR)
+  ORIGIN (HERE) a! !  0 (CUR) a! !  0 (SLOT) a! !  0 (NLIT) a! !
+  0 (FAILED) a! !  0 (ERRLINE) a! !  0 (LINE) a! !  0 (EOF) a! !
+  0 (PEEK) a! !  0 (RAW) a! ! ;
+
+\ the ROM: assemble the system's source from the console until its start
+\ runs it; on an error, stop at (ROM-FAILED) with the error's code in
+\ (FAILED) and its line in (ERRLINE), for the loader to report
+: (ROM)
+  (INIT)
+  L: (NEXT-TOKEN) if END  drop
+    (ONE)
+    (FAILED) a! @ if L0  drop  jump (ROM-FAILED)
+    L0: drop  jump L
+  END: drop
+    (FAILED) a! @ if NS  drop  jump (ROM-FAILED)
+    NS: drop  ERR-NO-START (FAIL)  jump (ROM-FAILED)
+
+: (ROM-FAILED)
+  H: jump H
+