refactor(V2): IBKR client — remove dead whitelist + max_cycles test

Code review polish (commit b9c58a3):
- Remove unused _AUTO_CONFIRM_WHITELIST (was scaffolding, never wired)
- Replace with policy comment documenting auto-confirm behavior
- New test: test_place_order_too_many_confirmations

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/cerbero_mcp/exchanges/ibkr/client.py

@@ -278,9 +278,9 @@ class IBKRClient:
 
     # ── Order writes ────────────────────────────────────────────
 
-    _AUTO_CONFIRM_WHITELIST = (
-        "outside RTH", "no market data", "you are submitting", "the contract",
-    )
+    # Auto-confirm policy: any IBKR warning that is NOT in _CRITICAL_WARNINGS
+    # is auto-confirmed up to _AUTO_CONFIRM_MAX_CYCLES times. Hardening to a
+    # strict whitelist (allow-list) is deferred — V1 trades safety for UX.
     _CRITICAL_WARNINGS = (
         "margin", "suitability", "credit", "rejected", "insufficient",
     )