feat(ECR-007): Wyckoff Live Structure with Confirmed/Live isolation

Add live.py lifecycle and event candidates; assemble confirmed vs live
in engine; Summary partition; execution_signal source=confirmed only.
Keep strategies untouched; do not lower Confirmed thresholds for Live.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/ENGINEERING_SPEC/ECR-007-wyckoff-live-structure.md

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+# ENGINEERING_SPEC — ECR-007 Wyckoff Live Structure
+
+**ECR:** ECR-007  
+**BD:** BD-2026-007  
+**Status:** Approved  
+
+## Intent
+
+Operators observe FORMING Wyckoff structure without feeding Live into execution.
+
+## Modules
+
+| Module | Role |
+|--------|------|
+| `events.py` / `range.py` | Confirmed facts |
+| `live.py` | Live candidates + confidence + lifecycle hint |
+| `engine.py` | Assemble cycles[].confirmed / .live |
+| `execution_signal_from_wyckoff` | Confirmed-only gate |
+
+## Lifecycle
+
+`UNKNOWN → FORMING → CONFIRMED → COMPLETED`
+
+## Non-goals
+
+strategies, maker, Live-as-signal, Confirmed threshold cuts.