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/core.v4

@@ -14,7 +14,7 @@
 \    1 Negative count        2 Not a number        3 Number too long
 \    4 Not a character       5 Dictionary full     6 Name missing
 \    7 Control structure mismatch     8 Control structures too deep
-\    9 Shift count out of range
+\    9 Shift count out of range      10 Protected word
 \   -1 the word has printed its own message
 
 macro SWAP   over push push drop pop pop   endmacro