chore(types): annotate four containers mypy could not infer

Each element type is taken from how the container is used rather than
guessed: kept_items is returned from trim_to_fit, whose signature is
already list[Any]; traces collects the dicts built at the append site;
expert_results and tool_outputs are keyed by tool_name (str) and hold
ToolReturnPart.content.

tracing_router.py needed `from typing import Any` added — it had no
import for it, so annotating without that would have traded a
var-annotated error for a name-defined one. Function-body variable
annotations are not evaluated at runtime, so this would not have raised;
mypy was the only thing that would have caught it.

90 errors -> 86.

Co-Authored-By: Claude <noreply@anthropic.com>

src/agents/tatlock.py

@@ -736,8 +736,8 @@ class TatlockAgent(AgentInterface):
 
         # Extract tool calls and results from the agent's messages
         tools_called = []
-        expert_results = {}
-        tool_outputs = {}
+        expert_results: dict[str, Any] = {}
+        tool_outputs: dict[str, Any] = {}
 
         # Parse through new messages to find tool calls and returns
         for msg in result.new_messages():