Move InstrumentServer to instruments/transport

InstrumentServer is a general-purpose SCPI-over-TCP server that can
host any device implementing the SCPIDevice protocol (process method).
Moving it from simulation/ to instruments/transport/ reflects this:
- simulation package now depends on instruments package
- InstrumentServer can host both virtual and real instrument adapters
- Added SCPIDevice Protocol for type-safe device registration

src/py_dvt_ate/instruments/transport/__init__.py

@@ -1,6 +1,11 @@
 """Transport layer for instrument communication.
 
 Provides connection abstractions for different backends:
+- TCP server for hosting SCPI instruments
 - TCP sockets (for simulation server)
 - PyVISA (for real instruments)
 """
+
+from py_dvt_ate.instruments.transport.server import InstrumentServer, SCPIDevice
+
+__all__ = ["InstrumentServer", "SCPIDevice"]

src/py_dvt_ate/instruments/transport/server.py

@@ -1,32 +1,55 @@
-"""Async TCP server for exposing virtual instruments over network.
+"""Async TCP server for exposing instruments over network.
 
-This module provides the InstrumentServer class that hosts virtual SCPI
+This module provides the InstrumentServer class that hosts SCPI
 instruments over TCP, allowing client applications to communicate using
 standard SCPI commands over a network connection.
+
+This is a general-purpose server that works with any object implementing
+the SCPIDevice protocol (having a process(command) -> str method).
 """
 
 from __future__ import annotations
 
 import asyncio
 import logging
-from typing import TYPE_CHECKING
+from typing import Protocol, runtime_checkable
 
-if TYPE_CHECKING:
+__all__ = ["InstrumentServer", "SCPIDevice"]
-    from py_dvt_ate.simulation.virtual.base import BaseInstrument
-
-# Re-export for type checking - actual import happens at runtime via registration
-__all__ = ["InstrumentServer"]
 
 logger = logging.getLogger(__name__)
 
 
+@runtime_checkable
+class SCPIDevice(Protocol):
+    """Protocol for SCPI-compatible devices.
+
+    Any object with a process method matching this signature can be
+    served by InstrumentServer.
+    """
+
+    def process(self, command: str) -> str:
+        """Process a SCPI command and return the response.
+
+        Args:
+            command: SCPI command string to process.
+
+        Returns:
+            Response string (may be empty for commands with no response).
+        """
+        ...
+
+
 class InstrumentServer:
-    """Async TCP server hosting virtual SCPI instruments.
+    """Async TCP server hosting SCPI instruments.
 
     Each instrument is assigned a port. Clients connect via TCP and send
     SCPI commands as newline-terminated strings. Responses are also
     newline-terminated.
 
+    This server can host any device implementing the SCPIDevice protocol,
+    including both virtual instruments (simulators) and adapters for
+    real hardware.
+
     Attributes:
         host: Host address to bind to.
     """
@@ -38,7 +61,7 @@ class InstrumentServer:
             host: Host address to bind to. Defaults to localhost.
         """
         self._host = host
-        self._instruments: dict[int, BaseInstrument] = {}
+        self._instruments: dict[int, SCPIDevice] = {}
         self._servers: list[asyncio.Server] = []
         self._running = False
 
@@ -52,12 +75,12 @@ class InstrumentServer:
         """Check if server is currently running."""
         return self._running
 
-    def register_instrument(self, port: int, instrument: BaseInstrument) -> None:
+    def register_instrument(self, port: int, instrument: SCPIDevice) -> None:
         """Register an instrument to be served on a specific port.
 
         Args:
             port: TCP port number to serve the instrument on.
-            instrument: Virtual instrument to serve.
+            instrument: SCPI device to serve (any object with process method).
 
         Raises:
             ValueError: If port is already registered.
@@ -76,7 +99,7 @@ class InstrumentServer:
             port,
         )
 
-    def get_instrument(self, port: int) -> BaseInstrument | None:
+    def get_instrument(self, port: int) -> SCPIDevice | None:
         """Get the instrument registered on a port.
 
         Args:
@@ -154,7 +177,7 @@ class InstrumentServer:
         self,
         reader: asyncio.StreamReader,
         writer: asyncio.StreamWriter,
-        instrument: BaseInstrument,
+        instrument: SCPIDevice,
         port: int,
     ) -> None:
         """Handle a client connection.

src/py_dvt_ate/simulation/__init__.py

@@ -2,9 +2,10 @@
 
 Provides virtual instruments backed by a coupled thermal-electrical
 physics engine. Used for development and testing without real hardware.
+
+Note: InstrumentServer has moved to py_dvt_ate.instruments.transport
 """
 
 from py_dvt_ate.simulation.server import ServerConfig, SimulationServer
-from py_dvt_ate.simulation.tcp_server import InstrumentServer
 
-__all__ = ["InstrumentServer", "ServerConfig", "SimulationServer"]
+__all__ = ["ServerConfig", "SimulationServer"]

src/py_dvt_ate/simulation/server.py

@@ -11,8 +11,8 @@ import logging
 import signal
 from dataclasses import dataclass
 
+from py_dvt_ate.instruments.transport import InstrumentServer
 from py_dvt_ate.simulation.physics.engine import PhysicsEngine
-from py_dvt_ate.simulation.tcp_server import InstrumentServer
 from py_dvt_ate.simulation.virtual.chamber import ThermalChamberSim
 from py_dvt_ate.simulation.virtual.multimeter import MultimeterSim
 from py_dvt_ate.simulation.virtual.power_supply import PowerSupplySim

tests/integration/test_tcp_server.py

@@ -9,9 +9,9 @@ import asyncio
 
 import pytest
 
+from py_dvt_ate.instruments.transport import InstrumentServer
 from py_dvt_ate.simulation.physics.engine import PhysicsEngine
 from py_dvt_ate.simulation.server import ServerConfig, SimulationServer
-from py_dvt_ate.simulation.tcp_server import InstrumentServer
 from py_dvt_ate.simulation.virtual.chamber import ThermalChamberSim
 from py_dvt_ate.simulation.virtual.multimeter import MultimeterSim
 from py_dvt_ate.simulation.virtual.power_supply import PowerSupplySim