feat(v4.0.0): POST for FORTH-79, from v3's cases; not passing yet

capsules/v4/post79.4th: 537 of v3's POST cases for the FORTH-79 Required
Word Set, each carrying what the hosted v3 binary did with the same line
(error or not, the stack, the length and checksum of what it printed).
Written by v4/tools/mkpost.py.  The harness is FORTH-79 plus the two
nucleus hooks.  docs/v4.0.0/NUCLEUS.md section 6.

- NODE-ERROR has a FORTH name: how a definition in FORTH raises an error
- the boot passes POST only on seeing its tally line with fail=0
- POST is not in the boot yet (V4_POST_AT_BOOT=0); make -C v4 post runs it

Result: tests=537 pass=439 fail=98.  The 98 are not yet sorted into v4
defects and differences needing a ruling; v4/README.md has a first reading.

Verified: make -C v4 test passes; hosted-check passes on three ISAs; clean
qemu with STARFORTH_V4=1 on amd64, aarch64 and riscv64 reaches ok> with the
same hashes as hosted (logs/20261005-1601xx..1604xx).  Nothing was typed at
a bare-metal prompt.

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

v4/capsule/quit.v4

@@ -68,6 +68,11 @@ macro R-CLEAR   RSTACK-DEPTH b! a !b   endmacro
 
 \ FORTH-79: clear the return stack, set execution mode, return control to
 \ the terminal; no message is given.  The data stack is left as it is.
+\ NODE-ERROR, by name: how a definition written in FORTH raises an error.
+\ A store of a code that is not zero is the trap of D-18 -- the word goes no
+\ further, the message for the code is printed (-1: the word has printed
+\ its own) and the line ends with ERROR.  The codes are listed in core.v4.
+header NODE-ERROR inline    : NODE-ERROR'   NODE-ERROR ;
 header (CATCH) inline       : (CATCH)'      (CATCH) ;
 header (EMIT-HOOK) inline   : (EMIT-HOOK)'  (EMIT-HOOK) ;