refactor(agents): organise the agents package by what each module holds

- tools.py: the analysts' data tools, previously seven modules under utils
- context.py (was agent_utils, without its tool re-exports), state.py, rating.py and structured.py sit beside schemas.py
- every role package has an __init__

tests/test_yahoo_snapshot.py

@@ -66,9 +66,7 @@ class TestVerifiedSnapshot:
 @pytest.mark.unit
 class TestTool:
     def test_tool_delegates_to_builder(self, monkeypatch):
-        from tradingagents.agents.utils.market_data_validation_tools import (
-            get_verified_market_snapshot,
-        )
+        from tradingagents.agents.tools import get_verified_market_snapshot
         monkeypatch.setattr(validator, "load_ohlcv", lambda s, d, fill_gaps=True: _sample_ohlcv())
         out = get_verified_market_snapshot.invoke(
             {"symbol": "COF", "curr_date": "2026-05-20"}