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/klammerset/base/base.k

@@ -0,0 +1,12 @@
+# Engine-tier fixture: the base of the klammerset COMBINING tests.  It owns the
+# target and the ".k" declaration that the two "house" sets override, so each
+# of them can require it and neither has to be loaded first on the command
+# line -- which is what makes command-line ORDER the only thing under test.
+#
+# The definitions sit in a :files entry rather than in this declaring file,
+# which is NOT a style choice: the already-loaded guard skips a repeated
+# declaration's :files, but the declaring file itself is read again every time
+# a :requires names it.  With the "@@@target fx" written here, requiring
+# "base" from two sets reads it twice and the second read is a fatal "Target
+# fx is already defined".  See case 21c, which pins that.
+@@@klammerset base | Base set for combining tests :date 2026-08-15 :files defs.k @@@

tst/klammerset/base/defs.k

@@ -0,0 +1,4 @@
+# The base set's definitions.  See base.k for why they are not in it.
+@@@target fx | Combining fixture target @@@
+@@who.k : Which klammerset supplied this definition @@
+@@who.fx :: BASE @@

tst/klammerset/decl.k

@@ -1,11 +0,0 @@
-# Engine-tier fixture: a klammerset with metadata, a dependency, an ordered
-# file list (klammers.k uses the target defined in base.k), and a trailing
-# definition that must load after the files (program order).
-@@@klammerset kit | Engine-test klammerset
-  :name Klammerset Integration Test
-  :author Klammertext tests
-  :date 2026-07-30
-  :requires util.k
-  :files base.k / klammers.k
-@@@
-@@after : AFTER @@

tst/klammerset/decl2.k

@@ -1 +0,0 @@
-@@@klammerset kit | Duplicate declaration of kit :files dup_only.k @@@

tst/klammerset/housea/housea.k

@@ -0,0 +1,9 @@
+# One of two independent sets of house overrides.  Both require "base" (loaded
+# once, whichever asks first) and both override the same klammer with ":::", so
+# the one written LAST on the command line is the one that wins.  Its own
+# klammer @a_only shows that the sets share one flat namespace rather than
+# each keeping its klammers to itself.
+@@@klammerset housea | House overrides A :requires base :date 2026-08-15 @@@
+@@who.fx ::: HOUSE-A @@
+@@a_only.k : A klammer only set A defines @@
+@@a_only.fx :: ONLY-A @@

tst/klammerset/houseb/houseb.k

@@ -0,0 +1,5 @@
+# The mirror image of housea; see the comment there.
+@@@klammerset houseb | House overrides B :requires base :date 2026-08-15 @@@
+@@who.fx ::: HOUSE-B @@
+@@b_only.k : A klammer only set B defines @@
+@@b_only.fx :: ONLY-B @@

tst/klammerset/kit/kit.k

@@ -0,0 +1,18 @@
+# Engine-tier fixture: a klammerset with metadata, a dependency, an ordered
+# file list (klammers.k uses the target defined in base.k), and a trailing
+# definition that must load after the files (program order).
+#
+# Laid out as <symbol>/<symbol>.k, which is what a symbol names: since
+# 2026-08-14 the command line takes symbols only, so a klammerset that
+# cannot be named by one cannot be loaded at all.  ":requires util" is a
+# SYMBOL, resolved on the search path (this directory is not util's parent,
+# so it is found at stage 2, KLAMMERTEXT_KLAMMERSETS); ":files" entries are
+# filenames, resolved against this file's directory.
+@@@klammerset kit | Engine-test klammerset
+  :name Klammerset Integration Test
+  :author Klammertext tests
+  :date 2026-07-30
+  :requires util
+  :files base.k / klammers.k
+@@@
+@@after : AFTER @@

tst/klammerset/needs_a/needs_a.k

@@ -0,0 +1,2 @@
+# Requires selfdef; paired with needs_b to make the diamond of case 21c.
+@@@klammerset needs_a | Requires selfdef :requires selfdef :date 2026-08-15 @@@

tst/klammerset/needs_b/needs_b.k

@@ -0,0 +1,2 @@
+# Requires selfdef; paired with needs_a to make the diamond of case 21c.
+@@@klammerset needs_b | Requires selfdef :requires selfdef :date 2026-08-15 @@@

tst/klammerset/selfdef/selfdef.k

@@ -0,0 +1,8 @@
+# A klammerset whose declaring file carries its own definitions (the
+# documented alternative to a :text option: program order plays that role).
+# Requiring it from two different sets reads this file twice, and the second
+# read of the @@@target is fatal.  Case 21c pins that defect; when it is
+# fixed, that case fails and must be rewritten.
+@@@klammerset selfdef | Definitions in the declaring file :date 2026-08-15 @@@
+@@@target fy | Self-defining fixture target @@@
+@@sd.fy : SELFDEF @@

tst/klammerset/sp/sp.k

@@ -0,0 +1,6 @@
+# The target and @greet come from kit, required by symbol; this set adds
+# only the file whose name contains a space (standalone "/" separator).
+@@@klammerset sp | Spacey filename in the list
+  :requires kit
+  :files space name.k
+@@@

tst/klammerset/spacey.k

@@ -1 +0,0 @@
-@@@klammerset sp | Spacey filename in the list :files base.k / space name.k @@@

tst/klammerset/wrap/dup.k

@@ -0,0 +1,6 @@
+# A declaration of the symbol "kit" from a file that is NOT kit/kit.k.
+# Since 2026-08-15 that is an ERROR: a klammerset that can be named is
+# identified by where it is, so a symbol names one file and one file declares
+# one symbol.  This fixture exists to prove the error; it formerly proved that
+# such a duplicate was tolerated and skipped.
+@@@klammerset kit | Duplicate declaration of kit :files dup_only.k @@@

tst/klammerset/wrap/wrap.k

@@ -0,0 +1,3 @@
+# Requires "kit" twice over: once by symbol, once through dup.k, which
+# re-declares it.  Loading "wrap" is therefore an error now -- see dup.k.
+@@@klammerset wrap | Wrapper requiring kit twice :requires kit / dup.k @@@

tst/klammerset/wrapper.k

@@ -1 +0,0 @@
-@@@klammerset wrap | Wrapper requiring kit twice :requires decl.k / decl2.k @@@