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/agents/utils/rating.py

@@ -12,11 +12,9 @@ Centralising it here avoids drift between those call sites.
 from __future__ import annotations
 
 import re
-from typing import Tuple
-
 
 # Canonical, ordered 5-tier scale (most bullish to most bearish).
-RATINGS_5_TIER: Tuple[str, ...] = (
+RATINGS_5_TIER: tuple[str, ...] = (
     "Buy", "Overweight", "Hold", "Underweight", "Sell",
 )