fix(dataflows): map crypto to StockTwits/Reddit sentiment symbols

- crypto reached StockTwits as Yahoo's BTC-USD (404) instead of BTC.X, and Reddit
  searched the dashed pair that barely matches; both now resolve the base via a
  shared crypto_base() helper, restoring crypto sentiment
- also fixes a StockTwits resilience test class that pytest never collected #1113

tests/test_stocktwits_resilience.py

@@ -1,5 +1,9 @@
-"""StockTwits fetch degrades (never raises) on transport errors, including the
-http.client chunked-transfer exceptions that are not OSErrors (#1024)."""
+"""StockTwits fetch: transport-error resilience (#1024) and crypto symbol
+mapping (#1113).
+
+StockTwits lists crypto under ``<BASE>.X`` (Yahoo's ``BTC-USD`` 404s), and any
+transport error must degrade to a placeholder rather than raise.
+"""
 
 from __future__ import annotations
 
@@ -26,7 +30,7 @@ def _raise(exc):
 
 
 @pytest.mark.unit
-class StockTwitsResilienceTests:
+class TestStockTwitsResilience:
     @pytest.mark.parametrize(
         "exc",
         [
@@ -40,3 +44,34 @@ class StockTwitsResilienceTests:
             out = stocktwits.fetch_stocktwits_messages("NVDA")
         assert "unavailable" in out.lower()
         assert out.startswith("<stocktwits unavailable")
+
+
+@pytest.mark.unit
+class TestStockTwitsCryptoSymbols:
+    @pytest.mark.parametrize(
+        ("ticker", "expected"),
+        [
+            ("BTC-USD", "BTC.X"),
+            ("eth-usd", "ETH.X"),
+            ("SOL-USD", "SOL.X"),
+            ("BTCUSD", "BTC.X"),      # undashed broker form
+            ("BTC-USDT", "BTC.X"),    # stablecoin quote
+            ("AMD", "AMD"),
+            ("BRK-B", "BRK-B"),       # dashed class share: untouched
+            ("GOLD", "GOLD"),         # real equity (aliases elsewhere): untouched here
+            ("XYZ-USD", "XYZ-USD"),   # unknown base: not treated as crypto
+        ],
+    )
+    def test_symbol_mapping(self, ticker, expected):
+        assert stocktwits._stocktwits_symbol(ticker) == expected
+
+    def test_crypto_pair_requests_dot_x_endpoint(self):
+        seen = {}
+
+        def fake_urlopen(req, timeout=None):
+            seen["url"] = req.full_url
+            raise TimeoutError("stop after capturing the URL")
+
+        with patch.object(stocktwits, "urlopen", side_effect=fake_urlopen):
+            stocktwits.fetch_stocktwits_messages("BTC-USD")
+        assert "/symbol/BTC.X.json" in seen["url"]