Tiingo WebSocket streaming: re-enable the level-breach monitor

The monitor has been dead since the Oanda feed switch (Oanda's provider
does not stream). New config.json scalar data_providers.streaming selects
a tick-stream provider independent of the candle feed; telegram_bot
resolves it via _get_streaming_dp() (separate instance, candle cache
stays on the active provider) and falls back to the active provider when
unset — behavior is byte-identical to before when the key is absent.

TiingoDataProvider grows the two sanctioned streaming overrides:
supports_streaming=True and iter_ticks() on wss://api.tiingo.com/fx
(mid price only — the no-spread rule extends to the stream). Two
deliberate divergences from the TD reference implementation, both
because Tiingo authenticates inside the socket: server "E" messages
raise TiingoDataError (a swallowed auth error would end the generator
cleanly and reconnect-hammer with zero backoff), and on_connect fires on
the first received message rather than after the subscribe send. Field
order of quote frames was live-verified: ask is data[7], not data[6] as
the docs table suggests (data[6] is askSize).

make_data_provider(config, name=None) now takes an explicit provider
name; keyless streaming providers disable the monitor with one warning
instead of a traceback-per-minute loop.

Tests 266 → 273 (WS parser, ticker round-trip, streaming config scalar,
explicit-name dispatch, streaming-dp resolution, monitor auto-disable).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Nsd8HcrV67GbCZXxZEn1Ma

app_config.py

@@ -106,6 +106,7 @@ class AppConfig:
     telegram_channel_id: str = ""          # "" = channel feed disabled
     alert_min_quality: str = "C"
     active_provider: str = "twelve_data"
+    streaming_provider: Optional[str] = None   # None = active provider
     provider_settings: Dict[str, Dict[str, Any]] = field(default_factory=dict)
     scan_pairs: List[str] = field(default_factory=lambda: [XAUUSD])
     scan_timeframes: List[Timeframe] = field(default_factory=lambda: [
@@ -162,7 +163,8 @@ def load_app_config(path: str = CONFIG_PATH) -> AppConfig:
         app.active_provider = str(dp.get("active", app.active_provider))
         app.provider_settings = {}
         for name, block in dp.items():
-            if name == "active":
+            # "active" and "streaming" are reserved scalars, not blocks.
+            if name in ("active", "streaming"):
                 continue
             if not isinstance(block, dict):
                 raise AppConfigError(
@@ -172,6 +174,17 @@ def load_app_config(path: str = CONFIG_PATH) -> AppConfig:
             raise AppConfigError(
                 f'config.json: data_providers.active "{app.active_provider}" '
                 "has no matching provider block")
+        streaming = dp.get("streaming")
+        if streaming is not None:
+            if not isinstance(streaming, str):
+                raise AppConfigError(
+                    'config.json: data_providers.streaming must be a string '
+                    "(a provider name)")
+            if streaming not in app.provider_settings:
+                raise AppConfigError(
+                    f'config.json: data_providers.streaming "{streaming}" '
+                    "has no matching provider block")
+            app.streaming_provider = streaming
 
     scanning = raw.get("scanning", {})
     _check_keys(scanning, _KNOWN_SCANNING, '"scanning"')