feat: robust-momentum strategies live; fix live universe, lots and UI backtests

Strategies
- BarStrategy protocol (close/open/high/low/volume bars; row d uses bars
  through d-1) and RobustMomentumStrategy: overnight_recovery_top10 (US),
  lowrisk_momentum_top15 and lowbeta_sharpe_mom_top20 (CN), top-N with
  rank hysteresis, 10-day rebalance, weights drift between rebalances.
- trader: strategy_fields/strategy_bars/bar_session_weights; one signal
  path (_signals_for_sessions) replaces generate_target_weights.

Live fixes
- CSI 300 constituents come from China Securities Index's file; the
  Wikipedia table was 122 names off the real index.
- S&P 500 change log moved to "Historical components of the S&P 500".
- data_manager: tickers missing from a partial Yahoo batch are retried
  alone before being marked unavailable (CEG, GEV, SNDK ... were dropped).
  update() takes fields=[...] and stores high/low/volume panels.
- Whole-lot orders go to the nearest lot within cash (CN books held ~62%
  cash); held names are resized only beyond RESIZE_BAND (10%), so books no
  longer pay a ticket fee to trade daily drift.

Web backtests
- backtest_runner.py replaces the duplicated bridge/precompute code: PIT
  membership in both markets (data/csi300_history.json), stock universe
  limited to index members (ETFs and benchmarks in the shared panel were
  pickable), and the book kept like the live trader (simulate_live_book:
  signal timing, drift, order floor, resize band, fees on orders placed).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

universe.py

@@ -76,45 +76,70 @@ def get_sp500() -> list[str]:
 # Yahoo Finance format: Shanghai → XXXXXX.SS, Shenzhen → XXXXXX.SZ
 # Wikipedia CSI 300 page has a table with stock codes and exchanges.
 
+CSI300_CONS_URL = ("https://oss-ch.csindex.com.cn/static/html/csindex/public/uploads/"
+                   "file/autofile/cons/000300cons.xls")
+
+
+def _csi300_official() -> list[str]:
+    """Current constituents from China Securities Index's published file."""
+    req = urllib.request.Request(CSI300_CONS_URL, headers={"User-Agent": "Mozilla/5.0"})
+    with urllib.request.urlopen(req, timeout=30) as resp:
+        payload = resp.read()
+    df = pd.read_excel(io.BytesIO(payload), dtype=str)
+    code_col = next(c for c in df.columns if "Constituent Code" in c)
+    exch_col = next(c for c in df.columns if c.startswith("交易所Exchange"))
+    tickers = [f"{code}.{'SS' if '上海' in exch else 'SZ'}"
+               for code, exch in zip(df[code_col], df[exch_col])]
+    if len(tickers) < 250:
+        raise RuntimeError(f"CSI 300 file has only {len(tickers)} rows")
+    return sorted(set(tickers))
+
+
+def _csi300_latest_snapshot() -> list[str]:
+    with open(os.path.join(CACHE_DIR, "csi300_history.json")) as f:
+        snaps = json.load(f)["snapshots"]
+    return snaps[max(snaps)]
+
+
+def _csi300_wikipedia() -> list[str]:
+    tables = _fetch_html_tables("https://en.wikipedia.org/wiki/CSI_300_Index")
+    # The constituent table has ~300 rows and a "Ticker" column like "SSE: 600519"
+    df = next((t for t in tables if len(t) >= 200 and "Ticker" in t.columns), None)
+    if df is None:
+        raise RuntimeError("Could not find CSI 300 constituent table on Wikipedia")
+    tickers = []
+    for raw in df["Ticker"].astype(str):
+        parts = raw.split(":")
+        if len(parts) == 2 and parts[1].strip().isdigit():
+            suffix = ".SS" if parts[0].strip().upper() == "SSE" else ".SZ"
+            tickers.append(parts[1].strip() + suffix)
+    return sorted(set(tickers))
+
+
 def get_csi300() -> list[str]:
-    """Fetch current CSI 300 constituents from Wikipedia."""
+    """Current CSI 300 constituents.
+
+    Source order: China Securities Index's published constituent file, then
+    the latest snapshot in data/csi300_history.json, then Wikipedia (whose
+    table lagged the real index by ~60 names in 2026).
+    """
     cached = _read_cache("csi300")
     if cached:
         print(f"--- Loaded CSI 300 universe from cache ({len(cached)} tickers) ---")
         return cached
 
-    print("--- Fetching CSI 300 constituents from Wikipedia ---")
-    url = "https://en.wikipedia.org/wiki/CSI_300_Index"
-    tables = _fetch_html_tables(url)
-
-    # Find the constituent table — it has ~300 rows and a "Ticker" column
-    # with format like "SSE: 600519" or "SZSE: 300750"
-    df = None
-    for t in tables:
-        if len(t) >= 200 and "Ticker" in t.columns:
-            df = t
-            break
-
-    if df is None:
-        raise RuntimeError("Could not find CSI 300 constituent table on Wikipedia")
-
-    tickers = []
-    for _, row in df.iterrows():
-        raw = str(row["Ticker"])  # e.g. "SSE: 600519" or "SZSE: 300750"
-        parts = raw.split(":")
-        if len(parts) != 2:
+    for label, source in (("csindex.com.cn", _csi300_official),
+                          ("stored CSI 300 history", _csi300_latest_snapshot),
+                          ("Wikipedia", _csi300_wikipedia)):
+        try:
+            tickers = source()
+        except Exception as exc:  # noqa: BLE001 — fall through to the next source
+            print(f"--- CSI 300 from {label} failed: {exc} ---")
             continue
-        exchange_prefix = parts[0].strip().upper()
-        code = parts[1].strip()
-        if not code.isdigit():
-            continue
-        suffix = ".SS" if exchange_prefix == "SSE" else ".SZ"
-        tickers.append(code + suffix)
-
-    tickers = sorted(set(tickers))
-    _write_cache("csi300", tickers)
-    print(f"--- Got {len(tickers)} CSI 300 tickers ---")
-    return tickers
+        _write_cache("csi300", tickers)
+        print(f"--- Got {len(tickers)} CSI 300 tickers from {label} ---")
+        return tickers
+    raise RuntimeError("No CSI 300 constituent source available")
 
 
 # ---------------------------------------------------------------------------