main/gb: --keys button-script harness + serial_no_eof for OSK testing

--keys "udlrabse." plays scripted joypad taps (each char = one button
held 10 frames then released 10, so the guest sees a clean edge); pairs
with --headless --shot to drive on-screen input and capture the result.
When --keys is active, serial-RX EOF stays pending instead of sending
$04, so a shell blocked on read waits for OSK input instead of exiting.

1 files changed, 5 insertions, 3 deletions

diff --git a/src/gb.c b/src/gb.c
index 3caa986..fc19e25 100644
--- a/src/gb.c
+++ b/src/gb.c
@@ -140,9 +140,11 @@ void gb_write(GB *gb, u16 addr, u8 val) {
                     gb->sc &= ~0x80;
                     gb_request_interrupt(gb, INT_SERIAL);
                 } else if (n == 0) {
-                    gb->sb = 0x04;         // EOF -> EOT (Ctrl-D)
-                    gb->sc &= ~0x80;
-                    gb_request_interrupt(gb, INT_SERIAL);
+                    if (!gb->serial_no_eof) {
+                        gb->sb = 0x04;     // EOF -> EOT (Ctrl-D)
+                        gb->sc &= ~0x80;
+                        gb_request_interrupt(gb, INT_SERIAL);
+                    }                      // else: stay pending (OSK provides input)
                 }
                 // n < 0 (EAGAIN on a live tty): stay pending, poll again
             }