Deliver the keys that are not characters

An arrow key has never reached this machine. Voyager threw it away for want of
anywhere to put it, and a terminal sent ESC [ A, which arrived in the middle of
whatever was being read and made it unrecognisable - typing Up at the CosmOS
prompt put three bytes in the command line and got "I do not know".

So the console names them: one byte each, 0x80 upward, above ASCII so nothing
written before them can collide. Up, Down, Left, Right, Home, End and forward
Delete, with room above for the paging and function keys.

The console normalises, which is what it already does. Behind a window it turns
the key somebody pressed into a byte; on a terminal it turns the sequence into
the same byte. That is the act it has always performed on Return and Backspace,
one layer further along, and it is why a program need not know which of the two
it is talking to. What a key MEANS is not the console's business - that belongs
to whoever is reading, the same way what is on a disk belongs to the system and
what a drive is belongs to the machine.

Translated only when standard input really is a terminal. Nothing else sends
these sequences, a pipe holds exactly the bytes somebody put in it, and it keeps
the Escape-or-Up timing problem out of every test here: a test writes the key
values themselves. Line mode drops them, in both front ends, because line mode
delivers characters and a line somebody else has finished editing cannot be
moved about in.

Press.sbx says what it was handed, in hexadecimal and by name, and reads a line
before it reads keys so both halves of that rule are checked. Two recordings,
one fed as standard input and one as a keyboard, agreeing byte for byte; each
break fails exactly one of them. Three checks in terminal.sh type real escape
sequences at a pseudo-terminal, which is the only place they are ever read as
sequences: that they arrive as keys, that Escape alone is still Escape, and that
a character typed straight after an escape is held rather than swallowed.

Five recordings re-blessed for Press.sbx appearing on the shared disk, and the
whole of that diff is the file's own line and the counts above it.

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

Tests/manifest

@@ -294,6 +294,17 @@ cosmosSnake          | CosmOS/Source/cosmos.asm           | run      | cosmosSna
 # console's slot at FE00 is zero again, and CosmOS's own disk handler further along is
 # untouched by a program having installed over the top of it.
 cosmosKeys           | CosmOS/Source/cosmos.asm           | run      | cosmosKeys.in      | -     | disks/cosmos.img
+# The keys that are not characters, both halves of the rule in one run: a line read in line
+# mode with an arrow key in the middle of it, which arrives with the arrow dropped because
+# line mode delivers characters, and then the same keys in key mode where they are what the
+# program asked for. Fed as STANDARD INPUT, so the console is reading bytes that are exactly
+# what is in the file - no terminal is involved and no escape sequence is translated, which
+# is what makes an arrow key testable at all.
+cosmosPress          | CosmOS/Source/cosmos.asm           | run      | cosmosPress.in     | -     | disks/cosmos.img
+# The same program and the same keys, fed as a KEYBOARD instead. That is the other front
+# end - the window's path through the gatherer - and it has its own copy of the line mode
+# rule, so it needs its own test. The two recordings should agree, which is the point.
+cosmosPressKeys      | CosmOS/Source/cosmos.asm           | run      | -                  | -     | disks/cosmos.img | cosmosPress.in
 # The shell taking things off a disk and calling them something else, which is the last of
 # CosmOS's original four verbs to be built and the first time anything has changed a disk
 # from the shell. Its own image, because it changes what is on it: a fixture named with a