feat(stock-lab): Screener 엔진 + combine + ScreenerResult + 노드 레지스트리

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

stock-lab/app/test_screener_engine.py

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+import datetime as dt
+import pandas as pd
+import pytest
+
+from app.screener.engine import ScreenContext, Screener, combine
+from app.screener.nodes.hygiene import HygieneGate
+from app.screener.nodes.foreign_buy import ForeignBuy
+from app.screener.nodes.momentum import Momentum20
+from app.screener._test_fixtures import make_master, make_prices, make_flow, make_kospi
+
+
+def _ctx(master, prices, flow):
+    return ScreenContext(master=master, prices=prices, flow=flow,
+                         kospi=make_kospi(days=260),
+                         asof=dt.date(2026, 5, 12))
+
+
+def test_combine_weighted_average():
+    scores = {
+        "foreign_buy": pd.Series({"A": 80, "B": 20}),
+        "momentum":    pd.Series({"A": 60, "B": 40}),
+    }
+    weights = {"foreign_buy": 2.0, "momentum": 1.0}
+    out = combine(scores, weights)
+    # A: (80*2 + 60*1)/3 = 73.33
+    assert abs(out["A"] - 73.333) < 0.1
+    assert abs(out["B"] - 26.666) < 0.1
+
+
+def test_combine_all_zero_weight_raises():
+    scores = {"foreign_buy": pd.Series({"A": 80})}
+    with pytest.raises(ValueError, match="no active"):
+        combine(scores, {"foreign_buy": 0})
+
+
+def test_screener_run_end_to_end():
+    asof = dt.date(2026, 5, 12)
+    master = make_master(["GOOD", "SMALL"],
+                         market_caps={"GOOD": 200_000_000_000, "SMALL": 1_000_000_000})
+    prices = make_prices(["GOOD", "SMALL"], days=260, asof=asof, trend_pct=0.1)
+    flow = make_flow(["GOOD", "SMALL"], days=260, asof=asof,
+                     foreign_per_day={"GOOD": 100_000_000, "SMALL": 0})
+    ctx = _ctx(master, prices, flow)
+
+    screener = Screener(
+        gate=HygieneGate(),
+        score_nodes=[ForeignBuy(), Momentum20()],
+        weights={"foreign_buy": 1.0, "momentum": 1.0},
+        node_params={"foreign_buy": {"window_days": 5}, "momentum": {"window_days": 20}},
+        gate_params={**HygieneGate.default_params, "min_listed_days": 0},
+        top_n=10,
+    )
+    result = screener.run(ctx)
+    assert result.survivors_count == 1                  # SMALL은 게이트 탈락
+    assert result.ranked.index[0] == "GOOD"