fix: bound task failures and release stalled workers

artemis/mcp/observation.py

@@ -22,9 +22,12 @@ Validator -- which runs its own UI-change polling -- simply never calls it.
 
 import asyncio
 import base64
+from io import BytesIO
 import time
+from PIL import Image
 
 from artemis.config import get_temp_dir
+from artemis.config.settings import settings
 from artemis.context import ArtemisContext
 from artemis.controllers.unified_controller import UnifiedMobileController
 from artemis.mcp.action_types import ActionCode, ObserveResult
@@ -34,7 +37,29 @@ from artemis.utils.visualization import format_minimal_list_with_elements
 
 logger = get_logger(__name__)
 
-__all__ = ["observe"]
+__all__ = ["observe", "require_observation", "DeviceObservationError"]
+
+
+class DeviceObservationError(RuntimeError):
+    """A live device could not be observed after bounded recovery."""
+
+
+async def require_observation(
+    ctx: ArtemisContext, controller: UnifiedMobileController, settle_ms: int = 400
+) -> tuple[ObserveResult, bytes | None]:
+    """Recover observation without spending model calls on unavailable screens."""
+    last = "设备未返回有效画面"
+    for attempt in range(settings.ARTEMIS_OBSERVATION_MAX_ATTEMPTS):
+        observation, image = await observe(ctx, controller, settle_ms=settle_ms)
+        if observation.ok:
+            return observation, image
+        last = observation.message
+        logger.warning(
+            f"设备观测恢复 {attempt + 1}/{settings.ARTEMIS_OBSERVATION_MAX_ATTEMPTS}：{last}"
+        )
+    raise DeviceObservationError(
+        f"设备观测失败（已尝试 {settings.ARTEMIS_OBSERVATION_MAX_ATTEMPTS} 次）：{last}"
+    )
 
 
 async def observe(
@@ -60,9 +85,19 @@ async def observe(
             await asyncio.sleep(settle_ms / 1000.0)
         else:
             logger.info("Retrieving screen data directly (skip settling)...")
-        device_data = await controller.get_screen_data()
+        device_data = await asyncio.wait_for(
+            controller.get_screen_data(), timeout=settings.ARTEMIS_OBSERVATION_TIMEOUT_SECONDS
+        )
         screenshot_bytes = base64.b64decode(device_data.base64)
+        with Image.open(BytesIO(screenshot_bytes)) as image:
+            if min(image.size) <= 1:
+                raise ValueError("设备截图为占位图，当前画面不可用")
+            image.verify()
     except Exception as e:
+        if isinstance(e, TimeoutError):
+            e = TimeoutError(
+                f"设备屏幕观测超时（{settings.ARTEMIS_OBSERVATION_TIMEOUT_SECONDS:g} 秒）"
+            )
         logger.error(f"Failed to capture screen state: {e}")
         return (
             ObserveResult(