fix(orders): arm strategy.exit trailing stop via trail_price (absolute activation)

[luisleo526]

Problem

The engine armed a strategy.exit trailing stop only when trail_points (an entry-relative tick offset) was set. A trail specified via trail_price (an absolute activation price level) — the other form Pine's strategy.exit accepts — was silently dropped: PendingOrder never carried trail_price, and every trail predicate (compute_exit_trail_state, the sort/classify/evaluate fill paths) keyed has_trail solely on trail_points. So strategy.exit(trail_price=close, trail_offset=...) produced no trailing exit at all.

Fix

• Add a default-NaN trail_price to PendingOrder (default-initialized so direct constructions that never assign it can't read an indeterminate value through the trail predicates).
• Persist trail_price in strategy_exit; initialize it to NaN in the other order constructors.
• Arm the trail on (trail_points || trail_price) across compute_exit_trail_state, sort_exit_siblings_by_path_fill, sort_orders_by_fill_phase, classify_order_eligibility, evaluate_fill_price, and the no-trail path metric.
• compute_exit_trail_state sets the activation level from trail_price as an absolute level (no entry-relative tick rounding); trail_points keeps precedence when both are set.

No new C-ABI export (trail_price already flows into strategy_exit from codegen; it was simply ignored).

Validation

	result
legalrice2697-nse-elite match vs TV	50.0% → 99.7% (359/360, price-exact 100%)
corpus	251 excellent / 1 anomaly / 0 fail (held)
ctest	76/76 incl. extended test_resolve_exit_trail_fills (trail_price long+short; reverting the arming → 4 CHECK failures)
check_c_abi_runtime.py	exit 0 (no symbol change)

🤖 Generated with Claude Code