refactor: unify agent history and harden runtime diagnostics

Preserve user guidance through history compression, stabilize Flash index targets, and retire withdrawn checks without applying stale verdicts.

Improve runtime diagnostics, tool responses, and history rendering. Simplify documentation and comments.

Validation: 2076 tests passed in the full suite; 381 affected tests and 26 frontend tests passed after cleanup. Ruff and the quality ratchet passed.

tests/unit/tools/test_save_note_tool.py

@@ -69,7 +69,7 @@ async def test_save_note_direct_execution_success(mock_ctx, tmp_path):
         key="test_note",
         content="Hello Artemis memory",
     )
-    assert result == "Successfully saved note to test_note.md."
+    assert result == "Saved note 'test_note'."
 
     note_path = Path(tmp_path) / "notes" / "test_note.md"
     assert note_path.exists()
@@ -84,7 +84,7 @@ async def test_save_note_callable_execution(mock_ctx, tmp_path):
         key="callable_note",
         content="Callable invocation test",
     )
-    assert result == "Successfully saved note to callable_note.md."
+    assert result == "Saved note 'callable_note'."
 
     note_path = Path(tmp_path) / "notes" / "callable_note.md"
     assert note_path.exists()
@@ -106,7 +106,7 @@ async def test_save_note_with_state_tool_message(mock_ctx, tmp_path):
 
     assert isinstance(result, ToolMessage)
     assert result.tool_call_id == "call_save_999"
-    assert result.content == "Successfully saved note to state_note.md."
+    assert result.content == "Saved note 'state_note'."
     assert result.status == "success"
 
     note_path = Path(tmp_path) / "notes" / "state_note.md"
@@ -141,7 +141,7 @@ async def test_get_save_note_tool_langchain_ainvoke(mock_ctx, tmp_path):
             "content": "Saved via LangChain BaseTool",
         }
     )
-    assert result == "Successfully saved note to lc_note.md."
+    assert result == "Saved note 'lc_note'."
 
     note_path = Path(tmp_path) / "notes" / "lc_note.md"
     assert note_path.exists()
@@ -160,7 +160,7 @@ async def test_get_save_note_tool_pure(mock_ctx, tmp_path):
             "content": "Saved via pure tool",
         }
     )
-    assert result == "Successfully saved note to pure_note.md."
+    assert result == "Saved note 'pure_note'."
 
     note_path = Path(tmp_path) / "notes" / "pure_note.md"
     assert note_path.exists()