feat(v4.0.0): the host node's stacks are 32 deep (D-17)

With the stacks counted and guarded (D-16) their size is a parameter of
the node.  The host node, which runs the interpreter and the compiler
under the user's programme, gets 32 values and 32 return entries; a mesh
node keeps the F18's 10 and 9.  Nothing else about the mechanism or any
word's definition changes.

- stack.h: V4_DATA_RING and V4_RET_RING are build parameters; the
  Makefile sets them for the host-node tests.
- tests/test_host_quit.c no longer assumes a size: it fills the stacks to
  whatever they are, and takes every exit with the return stack full.
- Measured on the host node now: 28 values on a line, 29 waiting between
  lines, words 31 deep from the prompt.

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

v4/tests/host_map.h

@@ -38,7 +38,7 @@
 #define CGVARS       (TOP - 48)                 /* (CG): codegen.v4, 14 cells */
 #define CVARS        (TOP - 62)                 /* (C): compile.v4, 10 cells */
 #define FVARS        (TOP - 105)                /* (F): forth.v4, 7 cells */
-#define SVARS        (TOP - 180)                /* (S): where PICK and ROLL set stack values aside, 10 cells */
+#define SVARS        (TOP - 540 - (v4_cell)V4_DATA_DEPTH)   /* (S): where PICK and ROLL set stack values aside, one cell for each cell of the stack */
 #define QVARS        (TOP - 52)                 /* (Q): quit.v4, 2 cells */
 
 /* buffers (word addresses; a byte address is four times this) */