feat: serialize public hardware execution

src/cognitive_agent/infrastructure/can/hardware.py

@@ -5,9 +5,12 @@ from __future__ import annotations
 import hashlib
 import hmac
 import os
+import threading
+import time
+from contextlib import contextmanager
 from dataclasses import dataclass
 from pathlib import Path
-from typing import Any, Callable
+from typing import Any, Callable, Iterator
 
 from cognitive_agent.infrastructure.firmware import (
     FIRMWARE_PROTOCOL_SIGNATURE,
@@ -36,6 +39,57 @@ class HardwareSafetyError(ValueError):
     """Raised before any CAN device is opened when a safety gate fails."""
 
 
+class HardwareBusyError(RuntimeError):
+    """Raised when another request already owns the single physical bench."""
+
+    def __init__(self, retry_after_seconds: int = 5) -> None:
+        self.retry_after_seconds = retry_after_seconds
+        super().__init__(
+            "真实座椅台架正在执行其他请求。为避免多人指令交叉，本次请求未进入CAN链路；"
+            "请等待当前动作完成后重试。"
+        )
+
+
+class HardwareExecutionCoordinator:
+    """Provide process-wide, fail-fast exclusive ownership of the physical bench."""
+
+    def __init__(self, retry_after_seconds: int = 5) -> None:
+        self.retry_after_seconds = retry_after_seconds
+        self._execution_lock = threading.Lock()
+        self._state_lock = threading.Lock()
+        self._active_since: float | None = None
+
+    @contextmanager
+    def reserve(self) -> Iterator[None]:
+        if not self._execution_lock.acquire(blocking=False):
+            raise HardwareBusyError(self.retry_after_seconds)
+        with self._state_lock:
+            self._active_since = time.monotonic()
+        try:
+            yield
+        finally:
+            with self._state_lock:
+                self._active_since = None
+            self._execution_lock.release()
+
+    def public_info(self) -> dict[str, Any]:
+        with self._state_lock:
+            active_since = self._active_since
+        return {
+            "busy": active_since is not None,
+            "active_for_ms": (
+                max(0, int((time.monotonic() - active_since) * 1000))
+                if active_since is not None
+                else 0
+            ),
+            "concurrency_policy": "single_flight_fail_fast",
+            "retry_after_seconds": self.retry_after_seconds,
+        }
+
+
+PHYSICAL_BENCH_COORDINATOR = HardwareExecutionCoordinator()
+
+
 def _env_bool(name: str, default: bool = False) -> bool:
     value = os.getenv(name)
     return default if value is None else value.strip().lower() in TRUE_VALUES