refactor(data): unify vendor errors under a VendorError hierarchy

Every condition where a vendor cannot return usable data now derives from a
single VendorError base (errors.py): NoMarketDataError, VendorRateLimitError,
and VendorNotConfiguredError (still a ValueError for back-compat). Vendor-named
errors subclass the generic bases, and the router catches the base types, so a
new vendor needs no new except clause. Not-configured now has explicit
try-next-vendor handling instead of falling through the generic catch-all. The
number of error types tracks the number of distinct router reactions, not the
number of causes.

tradingagents/dataflows/symbol_utils.py

@@ -23,29 +23,13 @@ from __future__ import annotations
 import logging
 import re
 
+# NoMarketDataError lives in the vendor-error taxonomy (errors.py); re-exported
+# here for the many call sites that import it alongside normalize_symbol.
+from .errors import NoMarketDataError as NoMarketDataError
+
 logger = logging.getLogger(__name__)
 
 
-class NoMarketDataError(Exception):
-    """Raised when a vendor returns no rows/records for a symbol.
-
-    Carries both the symbol the user requested and the canonical symbol the
-    vendor was actually queried with, so callers can build a clear message
-    instead of emitting a vendor-specific empty string into the data channel.
-    """
-
-    def __init__(self, symbol: str, canonical: str | None = None, detail: str = ""):
-        self.symbol = symbol
-        self.canonical = canonical or symbol
-        self.detail = detail
-        msg = f"No market data for {symbol!r}"
-        if canonical and canonical != symbol:
-            msg += f" (queried as {canonical!r})"
-        if detail:
-            msg += f": {detail}"
-        super().__init__(msg)
-
-
 # ISO-4217 codes common enough to appear in retail forex pairs. A bare
 # six-letter symbol whose halves are BOTH in this set is treated as a spot
 # forex pair and given Yahoo's ``=X`` suffix.