feat(fase-19): diagnostics detallados de rechazo + drawdown real

[guigerdts]

Summary

• RiskManager.approve() ahora retorna dicts estructurados en los 6 caminos de rechazo
• Peak-equity drawdown con mark-to-market real en Portfolio
• Engine y journal propagan el detalle de rechazo y direccion de posicion

Cambios

Archivo	Cambio
risk/manager.py	6 caminos de rechazo retornan dict con reason + detail
risk/portfolio.py	Peak-equity drawdown, MTM update_price()
core/engine.py	Propagacion defensiva de dicts de rechazo
core/journal.py	direction param, reason en rejected()
tests/test_engine.py	Tests actualizados
tests/test_max_positions_bug.py	Tests actualizados

Chain Context

Field	Value
Chain	FASE 19
Tracker PR	#3
Position	1 of 5
Base	tracker/fase-19
Depends on	None
Follow-up	PR2 #5
Review budget	106 / 400

Chain Overview

main
 └── #3 tracker/fase-19 (draft)
      └── 📍 #4 This PR — Diagnostics + Drawdown
           └── #5 PR2 — TradeTracker
                └── #6 PR3 — Dashboard
                     └── #7 PR4A — Cells Bidirectional
                          └── #8 PR4B — Bidirectional Completion

Scope

• Includes: Rejection diagnostics, peak-equity drawdown, journal direction params
• Excludes: TradeTracker, Dashboard, Bidirectional strategies