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/tests/host_map.h

@@ -35,6 +35,7 @@
 #define DVARS        (TOP - 32)                 /* (D): dict.v4, 5 cells */
 #define CGVARS       (TOP - 48)                 /* (CG): codegen.v4, 14 cells */
 #define CVARS        (TOP - 62)                 /* (C): compile.v4, 10 cells */
+#define QVARS        (TOP - 52)                 /* (Q): quit.v4, 2 cells */
 
 /* buffers (word addresses; a byte address is four times this) */
 #define CFS_W        (TOP - 96)                 /* the control-flow stack, 32 cells */
@@ -99,6 +100,7 @@ static int host_load(v4_text *tx, v4_node *n, const char *const *files, unsigned
     v4_text_constant(tx, "STATE", STATE);
     v4_text_constant(tx, "(C)", CVARS);
     v4_text_constant(tx, "(CFP)", CFP);
+    v4_text_constant(tx, "(Q)", QVARS);
     v4_text_constant(tx, "CFBASE", CFS_W);
     v4_text_constant(tx, "CFEND", CFS_W + CFS_CELLS);
     for (i = 0; i < count; i++) {