chore: tighten malformed tool-call guard wording

nanobot/agent/runner.py

@@ -952,7 +952,7 @@ class AgentRunner:
         retry_messages = list(messages)
         note = (
             "The previous model response attempted to call tools, but every tool call "
-            "was malformed: the tool_use blocks had missing/non-string name, id, or input. "
+            "was malformed: the tool_use blocks had missing or non-string tool names. "
             "Do not answer with a promise to use tools. Either call the required tools again "
             "using valid tool names from the provided tool list and JSON object inputs, or give "
             "a final answer only if no tool is required."

tests/agent/test_tool_hint.py

@@ -1,7 +1,7 @@
 """Tests for tool hint formatting (nanobot.utils.tool_hints)."""
 
-from nanobot.utils.tool_hints import format_tool_hints
 from nanobot.providers.base import ToolCallRequest
+from nanobot.utils.tool_hints import format_tool_hints
 
 
 def _tc(name: str, args) -> ToolCallRequest: