Implement thermal chamber SCPI commands

- TEMP:SETPOINT: Set/query target temperature
- TEMP:ACTUAL?: Query actual chamber temperature from physics engine
- TEMP:STAB?: Query temperature stability (within 0.5°C threshold)

src/py_dvt_ate/simulation/virtual/chamber.py

@@ -69,8 +69,27 @@ class ThermalChamberSim(BaseInstrument):
 
         Returns:
             Setpoint value for query, empty string for set command.
+
+        Raises:
+            ValueError: If setpoint argument is invalid.
         """
-        raise NotImplementedError("TEMP:SETPOINT not yet implemented")
+        if command.is_query:
+            return f"{self._setpoint:.2f}"
+
+        # Set command requires one argument
+        if not command.arguments:
+            raise ValueError("TEMP:SETPOINT requires a value")
+
+        try:
+            setpoint = float(command.arguments[0])
+        except ValueError:
+            raise ValueError(f"Invalid temperature value: {command.arguments[0]}")
+
+        self._setpoint = setpoint
+        if self._physics_engine is not None:
+            self._physics_engine.set_chamber_setpoint(setpoint)
+
+        return ""
 
     def _handle_temp_actual(self, command: SCPICommand) -> str:
         """Handle TEMP:ACTUAL? query.
@@ -80,16 +99,45 @@ class ThermalChamberSim(BaseInstrument):
 
         Returns:
             Actual chamber temperature.
+
+        Raises:
+            ValueError: If used as command (not query).
         """
-        raise NotImplementedError("TEMP:ACTUAL? not yet implemented")
+        if not command.is_query:
+            raise ValueError("TEMP:ACTUAL is query only")
+
+        if self._physics_engine is None:
+            # Return setpoint if no physics engine connected
+            return f"{self._setpoint:.2f}"
+
+        thermal_state = self._physics_engine.get_thermal_state()
+        return f"{thermal_state.chamber_temperature:.2f}"
 
     def _handle_temp_stab(self, command: SCPICommand) -> str:
         """Handle TEMP:STAB? stability query.
 
+        Temperature is considered stable when the actual chamber temperature
+        is within STABILITY_THRESHOLD of the setpoint.
+
         Args:
             command: Parsed SCPI command.
 
         Returns:
             "1" if stable, "0" if settling.
+
+        Raises:
+            ValueError: If used as command (not query).
         """
-        raise NotImplementedError("TEMP:STAB? not yet implemented")
+        if not command.is_query:
+            raise ValueError("TEMP:STAB is query only")
+
+        if self._physics_engine is None:
+            # Assume stable if no physics engine connected
+            return "1"
+
+        thermal_state = self._physics_engine.get_thermal_state()
+        error = abs(thermal_state.chamber_temperature - self._setpoint)
+
+        if error <= self.STABILITY_THRESHOLD:
+            return "1"
+        return "0"