feat: enrich daily bar schema with valuation/status fields + VWAP

Batch download now pulls baostock's preclose, turn, pctChg, tradestatus,
isST, and peTTM/pbMRQ/psTTM/pcfNcfTTM on top of OHLCV+amount, plus a
derived daily VWAP (amount/volume). VWAP is raw-price scale and not
comparable with adjusted OHLC under qfq/hfq — documented in the schema.

Richer fields live only in the batch path (download_daily_batch ->
download_universe); single-symbol download_daily keeps the legacy
8-column schema that test_downloader.py pins. Also flags intraday/L1-L2
microstructure data as a future phase in the README roadmap.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

pipeline/common/schema.py

@@ -4,15 +4,26 @@ from typing import Final
 
 # Required columns for data parquet files (daily bars, alternative data, etc.)
 DATA_COLUMNS: Final[list[str]] = [
-    "symbol_id",   # str: internal code like 'sh600000'
-    "symbol_name", # str: stock name like '浦发银行'
-    "date",        # date
-    "open",        # float64
-    "high",        # float64
-    "low",         # float64
-    "close",       # float64
-    "volume",      # float64 (shares)
-    "amount",      # float64 (turnover in yuan)
+    "symbol_id",     # str: internal code like 'sh600000'
+    "symbol_name",   # str: stock name like '浦发银行'
+    "date",          # date
+    "open",          # float64
+    "high",          # float64
+    "low",           # float64
+    "close",         # float64
+    "preclose",      # float64: previous trading day's close
+    "volume",        # float64 (shares)
+    "amount",        # float64 (turnover in yuan, raw/unadjusted)
+    "vwap",          # float64: daily VWAP = amount / volume. NB raw price scale —
+                     #   NOT comparable with adjusted OHLC under qfq/hfq.
+    "turn",          # float64: turnover rate (%)
+    "pctChg",        # float64: daily % change
+    "tradestatus",   # int: 1 = traded, 0 = suspended
+    "isST",          # int: 1 = ST/special-treatment, 0 = normal
+    "peTTM",         # float64: trailing-12m P/E
+    "pbMRQ",         # float64: P/B (most recent quarter)
+    "psTTM",         # float64: trailing-12m P/S
+    "pcfNcfTTM",     # float64: P/CF (net cash flow, TTM)
 ]
 
 # Required columns for alpha parquet files.