CosmOS lets every voice go when a program stops

A gate is a register on the sound device and only a program can drop one.
A program that has stopped cannot: it is gone. So a note left held
sustained until something else said otherwise, and nothing else did -
one program could leave the machine sounding for as long as it ran, with
nothing the person at it could do.

The shell already puts back the Stack, the vectors, the drive, the
working directory and the screen. This is the same list and the same
argument, and the fault path calls it too, for the stronger version of
the argument: a program that CRASHED is exactly the one that cannot tidy
up after itself, and a machine that will not stop humming is a poor place
to read an error message.

It does not make the device silent at once and does not pretend to.
Dropping a gate RELEASES a note rather than stopping it, so the patch's
release still runs. A bounded tail rather than an endless one is the part
the system can be responsible for without knowing what instrument the
program had built.

Hum exits while holding a note; Pause makes no sound and takes a couple
of million cycles, because the machine stops the moment the shell runs
out of input and a note quietened at that instant leaves no samples
behind to say whether it was. They are on a disk of their own so that a
fixture does not move the ten recordings that quote cosmos.img's listing.

THE CHECK CAUGHT ITSELF PASSING WRONGLY FIRST. Pause was missing from the
disk, the machine halted immediately, and the window that should have
held the tail was past the end of a render a twentieth of a second long -
an empty window's peak is nought, which is indistinguishable from silence.
So the sample count is asserted before anything is read from it. Verified
with break.sh: without the call the note is still ringing at 9869.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW

Tests/makedisks.sh

@@ -685,6 +685,23 @@ printf 'system /System/Boot/cosmos.bin\n' > "$WORK/lonely.cfg"
 "$TOOL" put "$DISKS/nofallback.img" "$WORK/lonely.cfg" /System/Boot/boot.cfg >/dev/null
 "$TOOL" bootstate "$DISKS/nofallback.img" 1 >/dev/null
 
+# ---- A program that stops while a note is still held ----
+#
+# Its own disk rather than a place on cosmos.img, because everything on that one appears in a
+# directory listing and ten recorded tests quote those. A fixture that exists to be run by one
+# check should not move ten others every time it changes size.
+"$TOOL" format "$DISKS/quiet.img" 128 2 >/dev/null
+"$TOOL" mkdir "$DISKS/quiet.img" /Apps >/dev/null
+"$ROOT/Assembler" -I "$ROOT/Programs/CosmOS/Source" \
+    "$ROOT/Programs/testPrograms/humTest.asm" -o "$WORK/Hum.sbx" >/dev/null
+"$TOOL" put "$DISKS/quiet.img" "$WORK/Hum.sbx" /Apps/Hum.sbx >/dev/null
+# And something silent to run after it, because the machine stops the moment the shell runs
+# out of input - a note quietened at that instant leaves no samples behind to say whether it
+# was quietened at all.
+"$ROOT/Assembler" -I "$ROOT/Programs/CosmOS/Source" \
+    "$ROOT/Programs/testPrograms/pauseTest.asm" -o "$WORK/Pause.sbx" >/dev/null
+"$TOOL" put "$DISKS/quiet.img" "$WORK/Pause.sbx" /Apps/Pause.sbx >/dev/null
+
 # ---- What a program made of it ----
 #
 # A status is only worth having if it survives the program that set it, so this runs three