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/graph/graph.py

@@ -718,6 +718,50 @@ async def _process_plan_write(
     return result
 
 
+async def _intercept_plan_write(
+    ctx: ArtemisContext,
+    original_tool,
+    args: dict,
+    tool_call_id,
+    state,
+    *,
+    declared_intent: bool,
+    content_after_fallback: str = "",
+):
+    """Run a note write and process any resulting task-plan changes."""
+    rejection = _reject_checker_note_write(args["key"], tool_call_id)
+    if rejection is not None:
+        return rejection
+    if args["key"] != "task_plan" or not ctx.data_engine:
+        return await invoke_tool_with_injection(
+            original_tool, args, tool_call_id, state, record_trace=False
+        )
+
+    task_plan_path = get_note_file_path(ctx.data_engine.base_dir, "task_plan")
+
+    content_before = ""
+    if task_plan_path.exists():
+        content_before = task_plan_path.read_text(encoding="utf-8")
+
+    result = await invoke_tool_with_injection(
+        original_tool, args, tool_call_id, state, record_trace=False
+    )
+
+    content_after = content_after_fallback
+    if task_plan_path.exists():
+        content_after = task_plan_path.read_text(encoding="utf-8")
+
+    return await _process_plan_write(
+        ctx,
+        state,
+        task_plan_path,
+        content_before,
+        content_after,
+        result,
+        declared_intent=declared_intent,
+    )
+
+
 def wrap_note_tool(ctx: ArtemisContext, original_tool):
 
     async def wrapped_note_tool(
@@ -727,37 +771,14 @@ def wrap_note_tool(ctx: ArtemisContext, original_tool):
         state: Annotated[State, InjectedState] = None,
     ):
         """Wrapped tool to intercept task plan updates."""
-        rejection = _reject_checker_note_write(key, tool_call_id)
-        if rejection is not None:
-            return rejection
-        args = {"key": key, "content": content}
-        if key != "task_plan" or not ctx.data_engine:
-            return await invoke_tool_with_injection(
-                original_tool, args, tool_call_id, state, record_trace=False
-            )
-
-        task_plan_path = get_note_file_path(ctx.data_engine.base_dir, "task_plan")
-
-        content_before = ""
-        if task_plan_path.exists():
-            content_before = task_plan_path.read_text(encoding="utf-8")
-
-        result = await invoke_tool_with_injection(
-            original_tool, args, tool_call_id, state, record_trace=False
-        )
-
-        content_after = content
-        if task_plan_path.exists():
-            content_after = task_plan_path.read_text(encoding="utf-8")
-
-        return await _process_plan_write(
+        return await _intercept_plan_write(
             ctx,
+            original_tool,
+            {"key": key, "content": content},
+            tool_call_id,
             state,
-            task_plan_path,
-            content_before,
-            content_after,
-            result,
             declared_intent=False,
+            content_after_fallback=content,
         )
 
     return StructuredTool.from_function(
@@ -786,36 +807,12 @@ def wrap_update_note_tool(ctx: ArtemisContext, original_tool):
         state: Annotated[State, InjectedState] = None,
     ):
         """Wrapped tool to intercept task plan updates via update_note."""
-        rejection = _reject_checker_note_write(key, tool_call_id)
-        if rejection is not None:
-            return rejection
-        args = {"key": key, "target": target, "replacement": replacement}
-        if key != "task_plan" or not ctx.data_engine:
-            return await invoke_tool_with_injection(
-                original_tool, args, tool_call_id, state, record_trace=False
-            )
-
-        task_plan_path = get_note_file_path(ctx.data_engine.base_dir, "task_plan")
-
-        content_before = ""
-        if task_plan_path.exists():
-            content_before = task_plan_path.read_text(encoding="utf-8")
-
-        result = await invoke_tool_with_injection(
-            original_tool, args, tool_call_id, state, record_trace=False
-        )
-
-        content_after = ""
-        if task_plan_path.exists():
-            content_after = task_plan_path.read_text(encoding="utf-8")
-
-        return await _process_plan_write(
+        return await _intercept_plan_write(
             ctx,
+            original_tool,
+            {"key": key, "target": target, "replacement": replacement},
+            tool_call_id,
             state,
-            task_plan_path,
-            content_before,
-            content_after,
-            result,
             declared_intent=True,
         )