feat(v4): the ROM reads numbers as text.c does

(NUMBER) ( -- n flag ), entry 2: decimal with a leading -, or hex after $;
1 a number, 0 not one, -1 one that does not fit a cell.  Every case is also
given to text.c, the oracle, at both widths.

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

capsules/v4/rom/main.f18

@@ -9,3 +9,4 @@
 : (ENTRIES)
   jump (KEY)                    \ 0   ( -- c )
   jump (TOKEN)                  \ 1   ( -- len )
+  jump (NUMBER)                 \ 2   ( -- n flag )

capsules/v4/rom/num.f18

@@ -0,0 +1,67 @@
+\ num.f18 -- the ROM reads numbers.
+\
+\ (NUMBER) ( -- n flag ) looks at the token (TOKEN) read, as v4/src/text.c's
+\ number_of does: decimal with an optional leading `-`, or hexadecimal after
+\ `$` (a-f in either case).  flag 1: the whole token is a number, n its
+\ value; 0: it is not one; -1: it is one, and does not fit a cell, read as
+\ signed or as unsigned.  A token that has a character that is not a digit
+\ is not a number, even when its digits so far did not fit.
+\
+\ State, in the ROM's area (MACHINE.md 2.1): (NBASE) 10 or 16, (NNEG) 1 after
+\ a `-`, (NI) the next character, (NU) the value so far, unsigned, (NBIG) 1
+\ once it has not fitted.  Width constants from the map: MSB, the cell's top
+\ bit; DEC-LIMIT, the largest unsigned cell over 10; DEC-NLAST, minus one
+\ more than its remainder; HEX-HIGH, the top four bits.  Uses A.  The
+\ token's characters are read with in.f18's (CHAR@).
+
+\ ( c -- d | -1 )   the digit c is in the base, or -1
+: (DIGIT)
+  dup -48 + -if D1  drop drop -1 ;            \ below '0'
+  D1: dup -10 + -if D2  drop push drop pop ;  \ '0' .. '9'
+  D2: drop drop
+    (NBASE) a! @ 16 xor if HEXL  drop drop -1 ;
+  HEXL: drop
+    dup -97 + -if LOW  drop
+    dup -65 + -if UP  drop drop -1 ;          \ below 'A'
+  UP: dup -6 + -if BAD  drop push drop pop 10 + ;
+  LOW: dup -6 + -if BAD  drop push drop pop 10 + ;
+  BAD: drop drop drop -1 ;
+
+\ ( d -- )   (NU) := (NU) * base + d, or (NBIG) := 1 if that does not fit
+: (ACC)
+  (NU) a! @
+  (NBASE) a! @ 16 xor if X16  drop
+  dup -if DPOS  drop  jump DBIG                 \ the top bit is set
+  DPOS: drop
+    dup inv 1 + DEC-LIMIT +  -if DLE  drop  jump DBIG
+  DLE: if DEQ  drop  jump MUL10
+  DEQ: drop  over DEC-NLAST +  -if DBIG3  drop  jump MUL10
+  DBIG3: drop
+  DBIG: 1 (NBIG) a! !  drop drop ;
+  MUL10: 2* dup 2* 2* + +  (NU) a! ! ;
+  X16: drop
+    dup HEX-HIGH and if HOK  drop  jump DBIG
+  HOK: drop  2* 2* 2* 2* +  (NU) a! ! ;
+
+\ ( -- n flag )
+: (NUMBER)
+  0 (NBIG) a! !  0 (NNEG) a! !  0 (NU) a! !  0 (NI) a! !  10 (NBASE) a! !
+  0 (CHAR@)
+  dup 36 xor if HEX  drop
+  dup 45 xor if NEG  drop drop  jump DIGITS
+  HEX: drop drop  16 (NBASE) a! !  1 (NI) a! !  jump DIGITS
+  NEG: drop drop  1 (NNEG) a! !  1 (NI) a! !
+  DIGITS: (NI) a! @  (TOKN) a! @  xor if NONE  drop
+  L: (NI) a! @ (CHAR@)  (DIGIT)
+    -if OK  drop  0 0 ;
+  OK: (ACC)
+    (NI) a! @ 1 + dup !  (TOKN) a! @ xor if DONE  drop  jump L
+  DONE: drop
+    (NBIG) a! @ if FITS  drop  0 -1 ;
+  FITS: drop  (NNEG) a! @ if POS  drop
+    (NU) a! @  -if NEGOK
+    MSB xor if EXACT  drop  0 -1 ;
+  EXACT: drop  MSB 1 ;
+  NEGOK: inv 1 +  1 ;
+  POS: drop  (NU) a! @  1 ;
+  NONE: drop  0 0 ;