feat(v4.0.0): every error is raised and ends the line (D-18)

Ruled 2026-10-04: guard all errors.  The errors that set NODE-ERROR and
let the line run on now stop it at once, with a message.

- A store of a non-zero code to NODE-ERROR is a trap, a sixth kind of
  fault: nothing after it executes, the return stack is emptied, and the
  data stack is left as the word left it.  Not attached, NODE-ERROR is
  plain memory, as the tests below the prompt use it.
- The capsule's words store a code where they stored -1, and the prompt's
  (RAISED) prints its message: Negative count, Not a number, Number too
  long, Not a character, Dictionary full, Name missing, Control structure
  mismatch, Control structures too deep.
- ' and COMPILE and [COMPILE] of a word that is not there say
  UNKNOWN WORD: 'xxx', as the interpreter does.
- tests: the trap in test_exec.c; every message from the prompt, with the
  rest of the line not run and the stack kept, in test_host_quit.c.

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

v4/capsule/dict.v4

@@ -41,7 +41,7 @@ macro OR  over inv and xor  endmacro
 \ they are storing in A while the space is taken: nothing of theirs is then
 \ on the data stack under (DP+), which itself needs three cells (D-2).
 
-: (DERR) ( -- 0 )      NODE-ERROR b! -1 !b  0 ;
+: (DERR) ( -- 0 )      NODE-ERROR b! 5 !b  0 ;        \ dictionary full
 
 \ ( n -- flag )   move DP by n bytes if it stays inside the dictionary space
 \ and say -1; otherwise leave it, set NODE-ERROR and say 0.  The two
@@ -66,7 +66,7 @@ header ,
   a!
   DP b! @b  3 + -4 and                       \ the next whole cell, as a byte address
   dup inv DLIMIT + -3 +  -if ROOM            \ DLIMIT - (it + 4)
-  drop drop  NODE-ERROR b! -1 !b ;
+  drop drop  NODE-ERROR b! 5 !b ;
   ROOM: drop  dup 4 + !b                     \ DP is past it
   4/ b!  a !b ;
 header C,
@@ -148,7 +148,7 @@ header HIDDEN
   0 ,  (D) a! @ ,  LATEST ,
   HERE (LATEST) a! ! ;
   FULL: drop ;                               \ (DP+) has set NODE-ERROR
-  EMPTY: drop  NODE-ERROR b! -1 !b ;
+  EMPTY: drop  NODE-ERROR b! 6 !b ;             \ name missing
 
 \ ---- looking a name up -----------------------------------------------------
 
@@ -186,5 +186,12 @@ header FIND
 \ ( -- addr )   FORTH-79: the parameter field address of the next word in the
 \ input stream.  Not found is an error: 0, and NODE-ERROR is set.  This is '
 \ when interpreting; compile.v4 adds what ' does when compiling.
+\ ( -- 0 )   say that the word WORD has just left is not known, as v3 does:
+\ UNKNOWN WORD: 'xxx'
+: (UNKNOWN)
+  $4E4B4E55 (EMIT4) $204E574F (EMIT4) $44524F57 (EMIT4) $27203A (EMIT4)
+  WBUF COUNT TYPE  39 EMIT CR
+  NODE-ERROR b! -1 !b  0 ;
+
 : (')    32 WORD (LOOKUP) if MISSING  jump PFA
-  MISSING: drop jump (DERR)
+  MISSING: drop jump (UNKNOWN)