added a state dumper for headless checks

src/cpu.rs

@@ -96,6 +96,15 @@ impl Cpu {
     pub fn set_nmi(&mut self) { self.nmi_pending = true; }
     pub fn set_irq(&mut self) { self.irq_pending = true; }
 
+    // read-only accessor for the headless state dump
+    pub fn pc(&self) -> u16 { self.pc }
+    pub fn a(&self) -> u8 { self.a }
+    pub fn x(&self) -> u8 { self.x }
+    pub fn y(&self) -> u8 { self.y }
+    pub fn sp(&self) -> u8 { self.sp }
+    pub fn p(&self) -> u8 { self.p }
+    pub fn cycles(&self) -> u64 { self.cycles }
+
     // shared interrumpt function
     fn interrupt(&mut self, bus: &mut impl Bus, vector: u16) -> u8 {
         self.push(bus, (self.pc >> 8) as u8);