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.

artemis/core/tool_declaration.py

@@ -18,7 +18,7 @@ from typing import Any
 
 
 class ToolDeclaration(dict):
-    """Standardized tool declaration adhering to JSON Schema format with property accessors."""
+    """OpenAI function schema with name, description and parameters properties."""
 
     def __init__(self, name: str, description: str, parameters: dict[str, Any]):
         super().__init__(
@@ -28,19 +28,16 @@ class ToolDeclaration(dict):
                 "description": description,
                 "parameters": parameters,
             },
-            name=name,
-            description=description,
-            parameters=parameters,
         )
 
     @property
     def name(self) -> str:
-        return self.get("name") or self.get("function", {}).get("name", "")
+        return self.get("function", {}).get("name", "")
 
     @property
     def description(self) -> str:
-        return self.get("description") or self.get("function", {}).get("description", "")
+        return self.get("function", {}).get("description", "")
 
     @property
     def parameters(self) -> dict[str, Any]:
-        return self.get("parameters") or self.get("function", {}).get("parameters", {})
+        return self.get("function", {}).get("parameters", {})