Support reverse Structure Event exits

[sybapp]

What to build

Add Strategy Spec and evaluator support for exiting a long LuxAlgo ICT/SMC position when a reverse bearish Structure Event Candidate Signal becomes available. This slice should keep stop loss as protective risk control and preserve intraday flat behavior.

Acceptance criteria

• A Strategy Spec can express reverse Structure Event exit rules for long positions using type: "signal" features.
• Bearish BOS, CHoCH, and MSS signals can trigger a next-bar exit for an open long position.
• Stop loss is evaluated before reverse-event exits when both could apply.
• maxBarsInTrade remains available as a safety exit.
• intradayFlat still closes any remaining position before RTH close.
• Tests cover reverse-event exit, stop-loss priority, max-bars fallback, and intraday flat fallback.

Blocked by

• Derive directional Structure Event signals from LuxAlgo graphics #23
• Extend Strategy Spec feature selectors for signal features #26