fix(interrupts): add explicit diverging loop to double_fault_handler

The x86_64 crate requires double fault handlers to have a diverging
return type (-> !). Added an explicit infinite loop after panic to
satisfy the type checker, even though the panic already ensures the
function never returns.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ryanbreen

kernel/src/interrupts.rs

@@ -148,7 +148,7 @@ extern "x86-interrupt" fn breakpoint_handler(stack_frame: InterruptStackFrame) {
 extern "x86-interrupt" fn double_fault_handler(
     stack_frame: InterruptStackFrame,
     _error_code: u64,
-) {
+) -> ! {
     // Log additional debug info before panicking
     log::error!("DOUBLE FAULT - Error Code: {:#x}", _error_code);
     log::error!("Instruction Pointer: {:#x}", stack_frame.instruction_pointer.as_u64());
@@ -162,6 +162,11 @@ extern "x86-interrupt" fn double_fault_handler(
     log::error!("Current page table frame: {:?}", frame);
 
     panic!("EXCEPTION: DOUBLE FAULT\n{:#?}", stack_frame);
+    // This is unreachable but needed to satisfy the type checker
+    #[allow(unreachable_code)]
+    loop {
+        x86_64::instructions::hlt();
+    }
 }