fix: kernel concurrency, interrupt context, and user VA safety

kernel/src/Drivers/PS2/Keyboard.hpp

@@ -39,7 +39,7 @@ namespace Drivers::PS2::Keyboard {
     void Initialize();
 
     // Interrupt handler -- called from IRQ dispatch (EOI is sent automatically)
-    void HandleIRQ(uint8_t irq);
+    void HandleIRQ(uint8_t irq, bool fromUser);
 
     // Public interface for consuming key events
     bool IsKeyAvailable();
@@ -52,4 +52,4 @@ namespace Drivers::PS2::Keyboard {
     // Inject a key event from an external source (e.g., USB HID keyboard)
     void InjectKeyEvent(const KeyEvent& event);
 
-};
+};