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/core.v4

@@ -6,6 +6,15 @@
 \
 \ Constants the loader supplies:  N-1 (cell bits - 1), NODE-ERROR, CONSOLE-TX,
 \ CONSOLE-RX, CONSOLE-STATUS, BASE.
+\
+\ ERRORS (D-18).  A word that finds an error takes its arguments off the stack
+\ and stores a code in NODE-ERROR.  On a node with a prompt that store is a
+\ trap: the word goes no further, and the prompt prints the message for the
+\ code and ERROR (quit.v4, (RAISED)).  The codes:
+\    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
+\   -1 the word has printed its own message
 
 macro SWAP   over push push drop pop pop   endmacro
 macro -      push inv pop + inv            endmacro      \ x y -- x-y
@@ -72,7 +81,7 @@ header C!
 \ ---- section 5.9: strings ------------------------------------------------
 header CMOVE
 : CMOVE ( src dst u -- )
-  -if OK  drop drop drop  NODE-ERROR b! -1 !b ;
+  -if OK  drop drop drop  NODE-ERROR b! 1 !b ;
   OK: if DONE  push
       over C@ over C!  1 + push 1 + pop  pop -1 +  jump OK
   DONE: drop drop drop ;
@@ -93,7 +102,7 @@ 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 ;
+  -if OK  drop drop  NODE-ERROR b! 1 !b ;
   OK: if DONE  over C@ EMIT  push 1 + pop  -1 +  jump OK
   DONE: drop drop ;