fix: mask all PIC IRQs after remap to prevent triple fault

Co-authored-by: aider (openrouter/moonshotai/kimi-k2.6) <aider@aider.chat>

platform_kernel.c

@@ -229,6 +229,8 @@ void kernel_main(void) {
     __asm__ volatile ("lidt %0" : : "m"(idt_ptr));
 
     pic_remap();
+    outb(0x21, 0xFF); // mask all IRQs on master
+    outb(0xA1, 0xFF); // mask all IRQs on slave
     pic_unmask_keyboard();
 
     __asm__ volatile ("sti");