fix: label broker sync events by actual execution broker (tradier stack)

Tradier stack emitted account/positions/orders events hardcoded as
broker_name=alpaca_paper while the executor filters snapshots by
client.broker_name (tradier) — position cap and re-entry block read zero
positions, and the dashboard showed 'Alpaca Paper' over real Tradier values.
Mode label now defaults from BROKER/TRADIER_ENV (tradier_live) instead of
alpaca_paper.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

trading_mode.py

@@ -5,7 +5,7 @@ from dataclasses import dataclass
 from typing import Literal, cast
 
 
-TradingMode = Literal["schwab_live", "alpaca_paper"]
+TradingMode = Literal["schwab_live", "alpaca_paper", "tradier_live", "tradier_sandbox"]
 
 
 @dataclass(frozen=True)
@@ -17,7 +17,14 @@ class TradingModeSettings:
         values = dict(os.environ)
         if env is not None:
             values.update(env)
-        mode = values.get("TRADING_EXECUTION_MODE", "alpaca_paper")
-        if mode not in {"schwab_live", "alpaca_paper"}:
-            mode = "alpaca_paper"
+        # BROKER=tradier swaps the execution client, so the default mode label
+        # must follow it — else the Tradier stack reports "alpaca_paper".
+        if values.get("BROKER", "alpaca").strip().lower() == "tradier":
+            sandbox = values.get("TRADIER_ENV", "sandbox").strip().lower() != "live"
+            default = "tradier_sandbox" if sandbox else "tradier_live"
+        else:
+            default = "alpaca_paper"
+        mode = values.get("TRADING_EXECUTION_MODE", default)
+        if mode not in {"schwab_live", "alpaca_paper", "tradier_live", "tradier_sandbox"}:
+            mode = default
         return cls(execution_mode=cast(TradingMode, mode))