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/tools/mobile/read_logs.py

@@ -21,7 +21,7 @@ from artemis.context import ArtemisContext
 from artemis.data_engine.trace import trace_langchain_tool
 from artemis.drivers.base import BaseDeviceDriver
 from artemis.graph.state import State
-from artemis.tools.base import ArtemisTool, ToolCategory, ToolRegistry
+from artemis.tools.base import ArtemisTool, ToolCategory
 from artemis.tools.mobile.log_utils import fetch_and_filter_logs
 from artemis.utils.logger import get_logger
 
@@ -108,7 +108,6 @@ class ReadLogsTool(ArtemisTool):
 read_logs = ReadLogsTool()
 ReadLogs = ReadLogsTool
 ReadLogsToolAlias = ReadLogsTool
-ToolRegistry.register(read_logs)
 
 
 def get_read_logs_tool(ctx: ArtemisContext) -> BaseTool: