feat(v4.0.0): the prompt -- QUIT, ABORT, ABORT" and ."

Layer 5 of the compiler capsule.  The host node is now started at QUIT and
left running: it prompts, reads a line from its console with QUERY,
interprets it, says " ok" or " ERROR", and goes round again.

- capsule/quit.v4: QUIT and ABORT (FORTH-79), ABORT" and (ABORT") as v3 has
  them, ." and (.") (FORTH-79).  Text is compiled as a counted string after
  the call; the run-time word returns to the cell after it.
- INTERPRET prints v3's messages before abandoning a line:
  UNKNOWN WORD: 'xxx' and xxx: compile-only.
- core.v4: CR SPACE COUNT TYPE, as DECOMPOSITION.md gives them.
- input.v4: WORD split so that (PARSE) can take text without skipping
  leading delimiters (." " is an empty string); EXPECT keeps its place in
  memory, so six values may wait on the stack while a line is typed.
- tests/test_host_quit.c: the node is fed characters and its output read;
  16 sessions are transcripts of the v3 binary.

QUIT stops the line from inside any word and says nothing; v3's goes on
with the line and cannot be compiled.  v3's compiled ABORT" crashes.

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

v4/capsule/core.v4

@@ -85,6 +85,24 @@ header KEY
   L: CONSOLE-STATUS b! @b  if WAIT  drop  CONSOLE-RX b! @b ;
   WAIT: drop  jump L
 
+header CR
+: CR    ( -- )         10 jump EMIT
+header SPACE
+: SPACE ( -- )         32 jump EMIT
+header COUNT
+: COUNT ( baddr -- baddr+1 c )   dup C@  push 1 + pop ;
+header TYPE
+: TYPE  ( baddr u -- )
+  -if OK  drop drop  NODE-ERROR b! -1 !b ;
+  OK: if DONE  over C@ EMIT  push 1 + pop  -1 +  jump OK
+  DONE: drop drop ;
+
+\ ( x -- )   up to four characters packed in one cell, the first in the low
+\ byte: how the capsule prints its own short messages, a literal at a time.
+: (EMIT4)
+  L: if DONE  dup EMIT  8/  jump L
+  DONE: drop ;
+
 \ ---- section 5.8: the number base ----------------------------------------
 : (BASE) ( -- b )      \ BASE, or 10 when it is outside 2 .. 36
   BASE b! @b  dup -2 + -if L1  drop drop 10 ;