fix: correct task scheduling and simplify agent internals

Fix queue cancellation, concurrency limits and worker status updates.

Use direct Explorer imports, split the Diagnoser loop into helpers and remove unused tool registration and prompt-builder code.

Correct model caching, endpoint selection and retry handling.

tests/tools/object_detector/test_object_detector_tools.py

@@ -14,7 +14,7 @@
 
 """Tests for object_detector universal tools."""
 
-from artemis.tools.base import ArtemisTool, ToolRegistry
+from artemis.tools.base import ArtemisTool
 from artemis.tools.object_detection_tool import (
     ObjectDetection,
     ObjectDetectionArgs,
@@ -29,8 +29,8 @@ from artemis.tools.object_detection_tool import (
 )
 
 
-def test_object_detector_tool_subclass_and_registry():
-    """Verify ObjectDetectionTool is an ArtemisTool subclass and registered in ToolRegistry."""
+def test_object_detector_tool_subclass():
+    """Verify ObjectDetectionTool is an ArtemisTool subclass."""
     assert issubclass(ObjectDetectionTool, ArtemisTool)
     assert issubclass(ObjectDetection, ArtemisTool)
     assert issubclass(ObjectDetectorTool, ArtemisTool)
@@ -51,8 +51,3 @@ def test_object_detector_tool_subclass_and_registry():
     assert operator_object_detection.name == "object_detection"
     assert operator_object_detection.category == "perception"
     assert operator_object_detection.args_schema == OperatorObjectDetectionArgs
-
-    # Registry lookup
-    reg_tool = ToolRegistry.get("object_detection")
-    assert reg_tool is not None
-    assert isinstance(reg_tool, ObjectDetectionTool)