An output policy for the three commands, and @cond as a true special form

A snapshot of the development tree.  The substantial changes since the last one:

COMMAND OUTPUT POLICY.  The three commands display text in exactly three cases,
and each owns a stream: LOGGING under "-v" greater than 0 and an ERROR before
termination go to STDERR; OUTPUT THE USER ASKED FOR goes to STDOUT.  For ktext
that output is a document, so "ktext doc.kt -d | ..." is now safe -- logging
used to share the stream and land inside the document.  A bare command prints
its usage and succeeds rather than failing.  Colour is emitted only to a
terminal, per stream, and NO_COLOR is honoured.

"-v 1" reports every decision whose outcome you could not have read off your own
input: the klammerset that was loaded and from which file, a font's directory, a
":files" name's file, how "-o" was expanded.  Higher levels are the trace.

The commands no longer warn and continue: an anomaly is an error, described with
its location.  Two exceptions remain, each for a stated reason -- a condition
that is expected and temporary by design, and a judgment that is a heuristic
rather than exact.

@cond IS NOW A TRUE SPECIAL FORM, resolved at APPLICATION time rather than when
the file is read.  Two consequences for a writer:

  * a state variable reaches the predicate.  "@@@state Flag :value true @@@
    @cond *Flag* | T | F @" renders "T"; it used to see the literal "*Flag*" and
    silently take the false branch.  The document now behaves like a klammer
    body, whose arguments are bound before its conditionals are decided.
  * nothing in a discarded branch happens -- it is not read, not evaluated, not
    expanded.  An @eval in the branch not taken used to run anyway.

Its predicate relation is total and strict: true, True, 1; false, False, 0, and
empty; anything else is an error at the @cond rather than silently false.

@eval REACHING OUTSIDE.  ":shell" and ":haskell" now keep the command's standard
error out of the document (it appears under "-v 1") and treat a nonzero exit as
an error naming what the command reported.  A command that exits nonzero on
purpose -- "grep" finding no match -- says so with "|| true".

KLAMMER SETS.  Several combine: "--klammersets a b c" loads all three in the
order given, sharing one namespace, with the definition modes deciding
collisions.  "none" means none and may not be combined with other symbols.  A
klammerset with symbol X is declared in a file X/X.k, which is what lets two
sets require the same third set without loading it twice.

TESTS.  Four new suites: the kdiag command's interface, the @eval primitive's
contract with the outside world, and verbosity at both tiers.  Three suites
that could not run on macOS at all now do.

Assembled from dev commit 6c8ee6c22fca.

tst/alone_test.sh

@@ -23,7 +23,7 @@
 # would take "some words" as the value and the alone value would never be
 # reached.  That is a definition-time error.
 #
-# Engine tier: these tests run with -k none and define their own argtypes
+# Engine tier: these tests run with --klammersets none and define their own argtypes
 # and klammers inline, so they do not depend on the Standard Klammer Set.
 #
 # Usage: ./alone_test.sh   (LSan suppressions come from env/runtime.env)
@@ -114,29 +114,29 @@ echo
 check_eq \
     " 1. name absent — the default" \
     "[0]" \
-    -k none -s "$DEPTH $DK @d@" -d
+    --klammersets none -s "$DEPTH $DK @d@" -d
 
 check_eq \
     " 2. name written alone — the type's alone value" \
     "[3]" \
-    -k none -s "$DEPTH $DK @d :n @" -d
+    --klammersets none -s "$DEPTH $DK @d :n @" -d
 
 check_eq \
     " 3. name written with a value — that value" \
     "[7]" \
-    -k none -s "$DEPTH $DK @d :n 7 @" -d
+    --klammersets none -s "$DEPTH $DK @d :n 7 @" -d
 
 # --- A type with an alone value but no default ---
 
 check_eq \
     " 4. no default declared — absent is empty" \
     "[]" \
-    -k none -s "$MARK $MK @m@" -d
+    --klammersets none -s "$MARK $MK @m@" -d
 
 check_eq \
     " 5. no default declared — alone still applies" \
     "[*]" \
-    -k none -s "$MARK $MK @m :c @" -d
+    --klammersets none -s "$MARK $MK @m :c @" -d
 
 # --- The alone value belongs to the type, so every parameter of that
 #     type gets it, and a parameter default does not disturb it ---
@@ -144,73 +144,73 @@ check_eq \
 check_eq \
     " 6. two parameters of one type share the alone value" \
     "[3][3]" \
-    -k none -s "$DEPTH @@d2 :a.depth :b.depth : [*a*][*b*] @@ @d2 :a :b @" -d
+    --klammersets none -s "$DEPTH @@d2 :a.depth :b.depth : [*a*][*b*] @@ @d2 :a :b @" -d
 
 check_eq \
     " 7. a parameter default overrides the type default, not the alone value" \
     "[5]|[3]" \
-    -k none -s "$DEPTH @@d3 :n.depth 5 : [*n*] @@ @d3@|@d3 :n @" -d
+    --klammersets none -s "$DEPTH @@d3 :n.depth 5 : [*n*] @@ @d3@|@d3 :n @" -d
 
 # --- bool: the convention that a bare boolean option means true ---
 
 check_eq \
     " 8. bool written alone is true" \
     "[true]" \
-    -k none -s '@@b :f.bool : [*f*] @@ @b :f @' -d
+    --klammersets none -s '@@b :f.bool : [*f*] @@ @b :f @' -d
 
 check_eq \
     " 9. bool written with false stays false" \
     "[false]" \
-    -k none -s '@@b :f.bool : [*f*] @@ @b :f false @' -d
+    --klammersets none -s '@@b :f.bool : [*f*] @@ @b :f false @' -d
 
 check_eq \
     "10. bool absent with no default is empty" \
     "[]" \
-    -k none -s '@@b :f.bool : [*f*] @@ @b@' -d
+    --klammersets none -s '@@b :f.bool : [*f*] @@ @b@' -d
 
 check_eq \
     "11. bool absent with a true parameter default" \
     "[true]" \
-    -k none -s '@@b :f.bool true : [*f*] @@ @b@' -d
+    --klammersets none -s '@@b :f.bool true : [*f*] @@ @b@' -d
 
 check_eq \
     "12. bool false explicitly against a true default" \
     "[false]" \
-    -k none -s '@@b :f.bool true : [*f*] @@ @b :f false @' -d
+    --klammersets none -s '@@b :f.bool true : [*f*] @@ @b :f false @' -d
 
 # --- The value reaching @eval ---
 
 check_eq \
     "13. python value of a bool written alone" \
     "True" \
-    -k none -s '@@b :f.bool : @eval repr(K.f) @ @@ @b :f @' -d
+    --klammersets none -s '@@b :f.bool : @eval repr(K.f) @ @@ @b :f @' -d
 
 check_eq \
     "14. python value of an absent bool" \
     "None" \
-    -k none -s '@@b :f.bool : @eval repr(K.f) @ @@ @b@' -d
+    --klammersets none -s '@@b :f.bool : @eval repr(K.f) @ @@ @b@' -d
 
 check_eq \
     "15. python value of a user type written alone" \
     "'3'" \
-    -k none -s "$DEPTH @@d4 :n.depth : @eval repr(K.n) @ @@ @d4 :n @" -d
+    --klammersets none -s "$DEPTH @@d4 :n.depth : @eval repr(K.n) @ @@ @d4 :n @" -d
 
 # --- Types that cannot delimit a bare option name ---
 
 check_error \
     "16. :alone refused on a type matching running text" \
     "cannot declare an :alone value" \
-    -k none -s '@@@argtype loose | anything at all :alone x @@@' -d
+    --klammersets none -s '@@@argtype loose | anything at all :alone x @@@' -d
 
 check_error \
     "17. :alone refused on an explicit match-everything pattern" \
     "cannot declare an :alone value" \
-    -k none -s '@@@argtype loose | anything :pattern (?:.^|\n)* :alone x @@@' -d
+    --klammersets none -s '@@@argtype loose | anything :pattern (?:.^|\n)* :alone x @@@' -d
 
 check_error \
     "18. an alone value must match its own type's pattern" \
     "does not match its own pattern" \
-    -k none -s '@@@argtype depth | a depth :pattern \d+ :alone many @@@' -d
+    --klammersets none -s '@@@argtype depth | a depth :pattern \d+ :alone many @@@' -d
 
 # --- Delimitation: an option value still runs to the next bar or option
 #     name, so text after a bare name is taken as the value and rejected
@@ -219,19 +219,19 @@ check_error \
 check_error \
     "19. text after a bare option name is taken as its value" \
     "does not match" \
-    -k none -s "$DEPTH $DK @d :n some words @" -d
+    --klammersets none -s "$DEPTH $DK @d :n some words @" -d
 
 check_eq \
     "20. a bar separates a bare option name from following text" \
     "[3]two" \
-    -k none -s "$DEPTH @@d5 :n.depth | t : [*n*]*t* @@ @d5 :n | two @" -d
+    --klammersets none -s "$DEPTH @@d5 :n.depth | t : [*n*]*t* @@ @d5 :n | two @" -d
 
 # --- A type with no alone value is unchanged: a bare name is empty ---
 
 check_eq \
     "21. bare option of a type with no alone value is empty" \
     "[]" \
-    -k none -s '@@s :t.word : [*t*] @@ @s :t @' -d
+    --klammersets none -s '@@s :t.word : [*t*] @@ @s :t @' -d
 
 echo
 echo "================================"