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, 1 insertions, 0 deletions

diff --git a/src/gb.h b/src/gb.h
index 7959e60..5192e85 100644
--- a/src/gb.h
+++ b/src/gb.h
@@ -113,6 +113,7 @@ struct GB {
     bool hdma_active;
 
     u64 cycles;        // total T-cycles elapsed
+    bool serial_no_eof; // if true, serial-RX EOF stays pending (don't send $04)
     bool serial_log;   // print serial output to stderr (blargg tests)
     int  serial_out_fd; // if >=0, transmitted serial bytes written here (stdout)
     int  serial_in_fd;  // if >=0, received serial bytes read here (stdin), else 0xFF