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, 5 insertions, 0 deletions

diff --git a/src/main.rs b/src/main.rs
index 2b1df77..9a901f5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -9,6 +9,7 @@ extern crate alloc;
 
 mod font;
 mod gop;
+mod interrupts;
 mod memory;
 mod ps2;
 mod serial;
@@ -127,6 +128,10 @@ pub extern "efiapi" fn efi_main(image_handle: Handle, system_table: *mut SystemT
     ps2::init();
     serial_println!("ps2: keyboard initialized");
 
+    // Interrupts — IDT, PIC, PIT timer, keyboard IRQ handler
+    interrupts::init();
+    serial_println!("intr: IDT loaded, PIC remapped, timer ~100 Hz");
+
     // Memory: the bump allocator was set up during capture_memory_map.
     // `alloc::Vec`, `alloc::String`, `format!` etc. are now usable.