fix(v4): the final review's six minors in the ROM boot

- Text after start is refused, as text.c refuses it: before it jumps, the
  ROM reads on to the end of the source; blanks, comments and the ends of
  blobs may follow, a token is ERR-AFTER (26), "text after start".
- A token too long where a name, a target or a value is wanted is "name
  too long", as text.c says: (MISSING) reports "missing" only when no error
  came first.  `", keeps "missing", which is text.c's word for both.
- text.c's "address out of range" names the address, not the value.
- The system's source files are one list, v4/sys_files.h: boot.c, the
  harness and the nucleus test are made from it.
- The ROM's error codes and words are one list, v4/rom_errors.h: boot.c's
  messages, host_map.h's ROM_ERR_* and mkmap's ERR-* are made from it.
- node.h says what v4_node_store does with a ROM address (nothing, as for
  any address outside RAM, D-14); test_host_rom_range pins it.

ROM: 2095 words, rom_hash 0x06d0dcb7a0cb41a1.  dict_hash unchanged,
0xe5a57f3eb72ff94a.  make -C v4 test test-32 hosted-check pass.  QEMU:
amd64, aarch64, riscv64 to ok>, POST 538/538, POST: PASSED.

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

capsules/v4/rom/dir.f18

@@ -44,7 +44,7 @@
 \ ( -- v 1 | 0 0 )   the next token as a VALUE
 : (NEXT-VALUE)
   (NEXT-TOKEN) if MISS  drop  jump (VALUE)
-  MISS: drop  ERR-MISSING (FAIL)  0 0 ;
+  MISS: drop  (MISSING)  0 0 ;
 
 : (H-CONSTANT)
   (IN-MACRO?) if OK  drop ;
@@ -56,7 +56,7 @@
   -if NUM  drop drop  ERR-BIG jump (FAIL)
   NUM: drop  (NAME-BACK)  2 jump (DEFINE)
   NAN: drop drop  ERR-VALUE jump (FAIL)
-  MISS: drop  ERR-MISSING jump (FAIL)
+  MISS: drop  jump (MISSING)
 
 : (H-SET)
   (IN-MACRO?) if OK  drop ;
@@ -66,7 +66,7 @@
   (NEXT-VALUE) if BADV  drop
   (NAME-BACK)  4 jump (DEFINE)
   BADV: drop drop ;
-  MISS: drop  ERR-MISSING jump (FAIL)
+  MISS: drop  jump (MISSING)
 
 \ here alone is not something to assemble: only a VALUE
 : (H-HERE)   ERR-TARGET jump (FAIL)
@@ -88,6 +88,7 @@
     (T2) a! @ (TOK) + a! @  (EMIT)
     (T2) a! @ 1 + !  jump L
   D: drop ;
+  \ text.c says "without a string, or one too long" for both: missing
   MISS: drop  ERR-MISSING jump (FAIL)
 
 \ store ADDR VALUE: ADDR must be in RAM, as text.c requires
@@ -113,7 +114,7 @@
   0 (RECN) a! !  0 (POOLN) a! !  0 (NREF) a! !  0 (NLAB) a! !
   0 (WNP) a! !  0 (NFOR) a! !  0 (RDEPTH) a! ! ;
 
-\ start NAME: the system's source has ended
+\ start NAME: the system's source has ended; NAME, a word, is where it starts
 : (H-START)
   (IN-MACRO?) if OK  drop ;
   OK: drop
@@ -130,9 +131,15 @@
   (FIND) if NOTW
   dup 2 + a! @ 1 xor if ISW  drop drop  jump NOTW0
   ISW: drop  3 + a! @  (T1) a! !
+  \ nothing may follow start but blanks, comments and the ends of blobs,
+  \ up to the end of all
+  A1: (TOKEN) if A2
+    drop  ERR-AFTER jump (FAIL)
+  A2: drop  (FAILED) a! @ if A3  drop ;
+  A3: drop  (EOF) a! @ if A1  drop
   (CLEAR)
   0 DSTACK-REG a! !  0 RSTACK-REG a! !
   (T1) a! @ push ;
   NOTW: drop
   NOTW0: ERR-START jump (FAIL)
-  MISS: drop  ERR-MISSING jump (FAIL)
+  MISS: drop  jump (MISSING)