interrupts: IDT, PIC remap, PIT timer, PS/2 keyboard IRQ

- IDT with 256 entries, loaded via lidt (CS read from current context)
- PIC 8259A remapped to vectors 32-47, timer+keyboard IRQs unmasked
- PIT channel 0 at ~100 Hz (mode 2, rate generator)
- PS/2 keyboard IRQ (IRQ1 → vector 33): reads port 0x60, pushes byte
  to lock-free SPSC ring buffer
- Timer IRQ (IRQ0 → vector 32): sends EOI, increments tick counter
- ps2::poll_key() now reads from ring buffer with cli/sti+hlt for
  race-free sleep (instead of busy-polling the data port)
- build.rs: use idiomatic Result<_, Box<dyn Error>> return type
- tools/qemu.sh: fix SC2207 shellcheck warning

1 files changed, 1 insertions, 1 deletions

diff --git a/tools/qemu.sh b/tools/qemu.sh
index 428954f..b75bed4 100755
--- a/tools/qemu.sh
+++ b/tools/qemu.sh
@@ -81,7 +81,7 @@ QEMU_CMD=(
 [ -n "$GUI_FLAG" ] && QEMU_CMD+=("$GUI_FLAG")
 if [ -n "$DEBUG_FLAG" ]; then
         # Split the flag string safely into words
-        read -ra dbg <<< "$DEBUG_FLAG"
+        read -ra dbg <<<"$DEBUG_FLAG"
         QEMU_CMD+=("${dbg[@]}")
 fi