feat(028-strategy-signals-contrib): add strategies __init__.py with public API exports

tradingagents/strategies/__init__.py

@@ -0,0 +1,22 @@
+"""Quantitative strategy signals framework.
+
+Based on:
+    Zura Kakushadze and Juan Andrés Serur,
+    "151 Trading Strategies",
+    Palgrave Macmillan, 2018.
+    SSRN: https://ssrn.com/abstract=3247865
+    DOI: 10.1007/978-3-030-02792-6
+"""
+
+from .base import BaseStrategy, Role, StrategySignal
+from .registry import compute_signals, format_signals_for_role, get_registry, reset_registry
+
+__all__ = [
+    "BaseStrategy",
+    "Role",
+    "StrategySignal",
+    "compute_signals",
+    "format_signals_for_role",
+    "get_registry",
+    "reset_registry",
+]