feat(v4.0.0): logging, as v3

- capsule/log.v4: the level constants LOG-ERROR .. LOG-DEBUG, LOG-LEVEL!
  and LOG-LEVEL@, LOG-ERROR" .. LOG-DEBUG" and LOG-ERROR-STR ..
  LOG-DEBUG-STR.  A message is printed if its level is at or below
  LOG-LEVEL, as v3's line -- colour, level, text -- without the time of
  day, which a node has not got.
- LOG-xxx" compiles like ." : the level, a call to (LOG"), the text.  SEE
  shows it as text.  COLD puts LOG-LEVEL back to LOG-INFO.
- tests/test_host_quit.c: ten transcripts of the v3 binary, every level
  at every setting.

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

v4/capsule/log.v4

@@ -0,0 +1,72 @@
+\ log.v4 -- logging, as v3: a message has a level, and is printed if the
+\ level is at or below LOG-LEVEL.
+\
+\ DECOMPOSITION.md 5.25: the level constants LOG-ERROR LOG-WARN LOG-INFO
+\ LOG-TEST LOG-DEBUG (0 .. 4), LOG-LEVEL! LOG-LEVEL@, LOG-ERROR" ... LOG-DEBUG"
+\ and LOG-ERROR-STR ... LOG-DEBUG-STR.  Part of the compiler capsule; rests
+\ on core.v4, codegen.v4 and quit.v4.
+\
+\ WHAT IS PRINTED is v3's line without its time of day, which a node has
+\ not got: the level's colour, the level's name and a colon, the colour off,
+\ the text, a new line --
+\     ESC [32m INFO:  ESC [0m text
+\ On the mesh a message will go to the recorder's log ring (5.25); until
+\ then it goes to the console.
+\
+\ Constants the loader supplies:
+\   (LOG-LEVEL)   word address of the variable: 2, LOG-INFO, at switch-on
+
+header LOG-ERROR inline   : LOG-ERROR   0 ;
+header LOG-WARN inline    : LOG-WARN    1 ;
+header LOG-INFO inline    : LOG-INFO    2 ;
+header LOG-TEST inline    : LOG-TEST    3 ;
+header LOG-DEBUG inline   : LOG-DEBUG   4 ;
+
+header LOG-LEVEL@
+: LOG-LEVEL@ ( -- n )   (LOG-LEVEL) a! @ ;
+\ ( n -- )   as v3: a level below 0 is 0, one above 4 is 4
+header LOG-LEVEL!
+: LOG-LEVEL!
+  -if POS  drop 0 jump SET
+  POS: dup -5 + -if BIG  drop jump SET
+  BIG: drop drop 4
+  SET: (LOG-LEVEL) a! ! ;
+
+\ ( baddr u level -- )   the message, if the level is at or below LOG-LEVEL
+: (LOG)
+  dup inv (LOG-LEVEL) a! @ + 1 + -if SHOW  drop drop drop drop ;     \ LOG-LEVEL - level
+  SHOW: drop
+  if P0  -1 + if P1  -1 + if P2  -1 + if P3  -1 + if P4
+  drop  jump OUT
+  P0: drop  $31335B1B (EMIT4) $6D (EMIT4)  $4F525245 (EMIT4) $203A52 (EMIT4)  $6D305B1B (EMIT4)  jump OUT
+  P1: drop  $33335B1B (EMIT4) $6D (EMIT4)  $4E524157 (EMIT4) $203A (EMIT4)  $6D305B1B (EMIT4)  jump OUT
+  P2: drop  $32335B1B (EMIT4) $6D (EMIT4)  $4F464E49 (EMIT4) $203A (EMIT4)  $6D305B1B (EMIT4)  jump OUT
+  P3: drop  $35335B1B (EMIT4) $6D (EMIT4)  $54534554 (EMIT4) $203A (EMIT4)  $6D305B1B (EMIT4)  jump OUT
+  P4: drop  $34335B1B (EMIT4) $6D (EMIT4)  $55424544 (EMIT4) $203A47 (EMIT4)  $6D305B1B (EMIT4)  jump OUT
+  OUT: TYPE  jump CR
+
+header LOG-ERROR-STR   : LOG-ERROR-STR ( baddr u -- )   0 jump (LOG)
+header LOG-WARN-STR    : LOG-WARN-STR  ( baddr u -- )   1 jump (LOG)
+header LOG-INFO-STR    : LOG-INFO-STR  ( baddr u -- )   2 jump (LOG)
+header LOG-TEST-STR    : LOG-TEST-STR  ( baddr u -- )   3 jump (LOG)
+header LOG-DEBUG-STR   : LOG-DEBUG-STR ( baddr u -- )   4 jump (LOG)
+
+\ ( level -- )   the run time of LOG-xxx" : the text is after the call, as
+\ for ." ; log it at that level and go on after it.
+header (LOG") compile-only
+: (LOG")
+  pop 4*  dup C@ over + 4/ 1 + push          \ level baddr      R: the cell after the text
+  COUNT  ROT  jump (LOG)
+
+\ ( level -- )   LOG-xxx" text"  logs the text -- now, if interpreting; when
+\ the word it is compiled into runs, if compiling.  (Q)+3 holds the level.
+: (LOG-QUOTE)
+  (Q)+3 a! !  34 (PARSE) drop
+  STATE a! @ if NOW
+  drop  (Q)+3 a! @ (LIT,)  &(LOG") (CALL,)  jump (STRING,)
+  NOW: drop  WBUF COUNT  (Q)+3 a! @  jump (LOG)
+header LOG-ERROR" immediate   : LOG-ERROR-QUOTE   0 jump (LOG-QUOTE)
+header LOG-WARN" immediate    : LOG-WARN-QUOTE    1 jump (LOG-QUOTE)
+header LOG-INFO" immediate    : LOG-INFO-QUOTE    2 jump (LOG-QUOTE)
+header LOG-TEST" immediate    : LOG-TEST-QUOTE    3 jump (LOG-QUOTE)
+header LOG-DEBUG" immediate   : LOG-DEBUG-QUOTE   4 jump (LOG-QUOTE)

v4/capsule/system.v4

@@ -141,7 +141,7 @@ header COLD
   (BOOT)+1 a! @  (LATEST) a! !
   (BOOT) a! @ 2/ 2/  FENCE a! !
   (LATEST) CONTEXT a! !  (LATEST) CURRENT a! !  0 VOC-LINK a! !
-  10 BASE a! !  0 SCR a! !  EMPTY-BUFFERS
+  10 BASE a! !  0 SCR a! !  2 (LOG-LEVEL) a! !  EMPTY-BUFFERS
   $54524F46 (EMIT4) $39372D48 (EMIT4) $6C6F4320 (EMIT4) $74532064 (EMIT4) $747261 (EMIT4) CR
   $74737953 (EMIT4) $69206D65 (EMIT4) $6974696E (EMIT4) $7A696C61 (EMIT4) $2E6465 (EMIT4) CR
   jump ABORT

v4/capsule/tools.fth

@@ -46,7 +46,8 @@ VARIABLE (SN)    \ how many lines
 \ ( addr -- )  after a call to addr: if it is one of the words that are
 \ followed by text, show the text and count its cells with the literals
 : (TEXT?)
-  DUP ['] (.") = OVER ['] (ABORT") = OR SWAP ['] (S") = OR IF
+  DUP ['] (.") = OVER ['] (ABORT") = OR OVER ['] (LOG") = OR
+  SWAP ['] (S") = OR IF
     (SP) @ (SLITS) @ + 4 *  COUNT  34 EMIT 2DUP TYPE 34 EMIT SPACE
     SWAP DROP 4 + 4 / (SLITS) +!
   THEN ;