Put a reset button on the case, and stop Escape closing the window

ESCAPE WAS A BUG I LEFT. This machine sends Escape to the console like any other key, and
Raylib closes a window on Escape unless it is told not to - so a program reading keys could
be ended by one of them, taking whatever was in memory with it. SetExitKey(KEY_NULL), and it
is a byte again.

F12 is the reset button. A button on the case rather than a key the machine can see: nothing
sends a function key to the console, so nothing can be surprised by one. It does what writing
MACHINE_RESET does, which is that the machine starts the way it started - the boot chain runs
again and finds whatever the disk now says to run.

Which is what makes a bare metal program escapable. Once puts a demo in front of the next
start and deletes the request before jumping, so a demo that has taken the whole machine is
one keypress from the system coming back, instead of closing the window and opening it again.

IT HAD TO REACH A MACHINE THAT IS WAITING, and that took two more things. A reset is acted on
between instructions, and a machine blocked on a key is part way through one - so the button
would have set a flag that nothing ever came along to notice, in exactly the situation a
reset button is for. The wait ends now: the console is told its input is over, which it is
for a machine about to stop existing.

And the reset puts the console's input back - nothing pushed back, no line half gathered, and
not at the end of input. That was already wrong before the button existed: a reset after the
input ran out left a console that had run out afterwards, so a machine could be restarted
once and then never typed at again.

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

Source/Emulator/io.c

@@ -631,6 +631,18 @@ static uint8_t pendingInterrupts[INTERRUPT_LINE_BYTES];
 // Whether somebody has asked the machine to start over, and taking that request away.
 static int resetWanted = 0;
 
+void requestReset(void) {
+    resetWanted = 1;
+}
+
+void consoleResetInput(void) {
+    consolePushback = -1;
+    consoleEnded = 0;
+    consoleLineLength = 0;
+    consoleLineAt = 0;
+    clearInterrupt(PORT_CONSOLE);
+}
+
 int takeResetRequest(void) {
     int wanted = resetWanted;
     resetWanted = 0;