chore(lint): make the repository ruff-clean under the strict select

Clear the deferred full-repo lint backlog so the whole tree passes the strict
ruff select (E,W,F,I,B,UP,C4,SIM). Mechanical fixes dominate: import sorting,
pep585/604 annotations, dropped dead imports, and whitespace. The few semantic
changes are behavior-preserving: declare __all__ on the agent_utils and
alpha_vantage re-export hubs; expand 'from x import *' to explicit names; use
immutable tuple defaults instead of mutable list defaults; contextlib.suppress
for try/except/pass; and narrow an over-broad assertRaises.

tradingagents/llm_clients/validators.py

@@ -2,7 +2,6 @@
 
 from .model_catalog import get_known_models
 
-
 # Providers whose model names are user-defined (local servers, relays, hosted
 # OpenAI-compatible endpoints serving many models), so any model string is
 # accepted without warning.