feat(v4.0.0): CASE, ['], S", WORDS, FORGET and FENCE

- compile.v4: CASE OF ENDOF ENDCASE, as v3 (they nest; a word out of
  place is a control structure mismatch); ['] and [LITERAL].
- quit.v4: S" and its run-time word; at the prompt the text is copied to
  PAD.
- capsule/system.v4: WORDS and VLIST; FORGET (FORTH-79), which gives the
  space back and will not remove a word below FENCE -- the capsule's own
  words -- where v3's FORGET DUP succeeds.
- tests/test_host_quit.c: ten more transcripts of the v3 binary, and
  nesting, the fence and the listing.

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

v4/capsule/system.v4

@@ -0,0 +1,45 @@
+\ system.v4 -- words about the dictionary as a whole: WORDS, FORGET, FENCE.
+\
+\ DECOMPOSITION.md 5.13 and 5.15.  Part of the compiler capsule; rests on
+\ dict.v4, quit.v4 and forth.v4.
+\
+\ Constants the loader supplies:
+\   FENCE   word address of the variable: FORGET will not remove an entry
+\           that starts below the address it holds
+
+header FENCE inline     : FENCE'  FENCE ;
+
+\ ( -- )   the names in the dictionary, the newest first, a blank after
+\ each, a new line whenever one has passed column 64.  Hidden entries -- a
+\ definition under way -- are not shown.  (Q)+0 is the column.
+header WORDS
+: WORDS
+  0 (Q) a! !
+  LATEST
+  L: if DONE
+     dup -3 + a! @ 2 and if SHOW  drop jump NXT
+     SHOW: drop
+       dup -2 + a! @ 4*  COUNT 31 and        \ xt baddr u
+       dup (Q) a! @ + 1 + !
+       TYPE SPACE
+       (Q) a! @ -64 + -if WRAP  drop jump NXT
+       WRAP: drop  CR  0 (Q) a! !
+     NXT: -1 + a! @  jump L
+  DONE: drop  jump CR
+header VLIST
+: VLIST   jump WORDS
+
+\ FORGET xxx   FORTH-79: remove xxx and every word defined after it.  The
+\ space they took is free again.  A word that is not there is an error, and
+\ so is one below FENCE, which is where the capsule's own words are (code
+\ 10, "Protected word").
+header FORGET
+: FORGET
+  32 WORD (LOOKUP) if MISSING
+  dup -2 + a! @                              \ xt name
+  dup FENCE a! @ inv + 1 + -if OK            \ name - fence
+    drop drop drop  NODE-ERROR b! 10 !b ;
+  OK: drop
+  4* DP a! !                                 \ the space from its name on
+  -1 + a! @ (LATEST) a! ! ;                  \ and the entry before it is the newest
+  MISSING: drop  (UNKNOWN) drop ;