Refactor DUTModel from Protocol to ABC for explicit interface implementation

src/py_dvt_ate/simulation/physics/models/base.py

@@ -1,15 +1,14 @@
-"""Base protocol for Device Under Test (DUT) models.
+"""Base interface for Device Under Test (DUT) models.
 
 Defines the interface that all DUT models must implement to integrate
 with the physics engine.
 """
 
-from typing import Protocol, runtime_checkable
+from abc import ABC, abstractmethod
 
 
-@runtime_checkable
-class DUTModel(Protocol):
-    """Protocol for DUT electrical/thermal models.
+class DUTModel(ABC):
+    """Abstract base class for DUT electrical/thermal models.
 
     DUT models encapsulate the temperature-dependent electrical behaviour
     of a device, enabling realistic simulation of thermal-electrical coupling.
@@ -18,8 +17,12 @@ class DUTModel(Protocol):
     All voltage parameters are in volts.
     All current parameters are in amps.
     All power parameters are in watts.
+
+    Implementations must inherit from this class and implement all abstract
+    methods.
     """
 
+    @abstractmethod
     def calculate_output_voltage(self, junction_temperature: float) -> float:
         """Calculate the output voltage at the given junction temperature.
 
@@ -29,8 +32,9 @@ class DUTModel(Protocol):
         Returns:
             Output voltage in volts.
         """
-        ...
+        pass
 
+    @abstractmethod
     def calculate_quiescent_current(self, junction_temperature: float) -> float:
         """Calculate the quiescent current at the given junction temperature.
 
@@ -40,8 +44,9 @@ class DUTModel(Protocol):
         Returns:
             Quiescent current in amps.
         """
-        ...
+        pass
 
+    @abstractmethod
     def calculate_power_dissipation(
         self,
         input_voltage: float,
@@ -58,4 +63,4 @@ class DUTModel(Protocol):
         Returns:
             Power dissipation in watts.
         """
-        ...
+        pass

src/py_dvt_ate/simulation/physics/models/ldo.py

@@ -7,6 +7,8 @@ and power dissipation calculations.
 
 from dataclasses import dataclass
 
+from py_dvt_ate.simulation.physics.models.base import DUTModel
+
 
 @dataclass(frozen=True)
 class LDOParameters:
@@ -35,7 +37,7 @@ class LDOParameters:
 REFERENCE_TEMPERATURE_C = 25.0
 
 
-class LDOModel:
+class LDOModel(DUTModel):
     """Temperature-dependent LDO voltage regulator model.
 
     Models the electrical behaviour of a linear voltage regulator with:
@@ -44,7 +46,7 @@ class LDOModel:
     - Dropout voltage that increases with temperature
     - Power dissipation from (Vin - Vout) × Iload + Vin × Iq
 
-    This class implements the DUTModel protocol.
+    This class implements the DUTModel interface.
     """
 
     def __init__(