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/option_set_test.sh

@@ -50,7 +50,7 @@ PRELUDE='@@@target fix | a fixture target @@@
 check_eq() {
     local name="$1" expected="$2" source="$3" target="${4:-fix}"
     local output status
-    output=$("$KTEXT" -k none -s "$PRELUDE
+    output=$("$KTEXT" --klammersets none -s "$PRELUDE
 $source" -t "$target" -d 2>&1)
     status=$?
     output=$(printf '%s' "$output" | tr -d '\n' | sed 's/^[[:space:]]*//; s/[[:space:]]*$//')
@@ -76,7 +76,7 @@ $source" -t "$target" -d 2>&1)
 check_fails() {
     local name="$1" needle="$2" source="$3"
     local output status
-    output=$("$KTEXT" -k none -s "$PRELUDE
+    output=$("$KTEXT" --klammersets none -s "$PRELUDE
 $source" -t fix -d 2>&1)
     status=$?
     if [ $status -eq 0 ]; then
@@ -98,11 +98,23 @@ $source" -t fix -d 2>&1)
 # check_warns NAME SUBSTRING SOURCE — SOURCE must be accepted, and its
 # combined output must contain SUBSTRING (used where a warning is expected
 # beside the result, so an exact comparison would test the warning's wording).
+# Since 2026-08-15 the override notice is reported at "-v 1" rather than
+# warned about: ":::" exists to override, so the notice fired on the sanctioned
+# use of a feature (see tst/deftype_test.sh's check_warn for the reasoning).
+# The default run must be SILENT and the notice must appear at "-v 1".
 check_warns() {
     local name="$1" needle="$2" source="$3"
-    local output status
-    output=$("$KTEXT" -k none -s "$PRELUDE
-$source" -t fix -d 2>&1)
+    local output status quiet
+    quiet=$("$KTEXT" --klammersets none -s "$PRELUDE
+$source" -t fix -d 2>&1 >/dev/null)
+    if [ -n "$quiet" ]; then
+        echo "${red}FAIL${reset} $name — the default run was not silent"
+        echo "       got: $(printf '%s' "$quiet" | head -1)"
+        FAIL=$((FAIL + 1))
+        return
+    fi
+    output=$("$KTEXT" --klammersets none -s "$PRELUDE
+$source" -t fix -d -v 1 2>&1)
     status=$?
     if [ $status -ne 0 ]; then
         echo "${red}FAIL${reset} $name — ktext exited $status"