Data Model: Order Management and Matcher

Scope

This state defines data model impact relative to 007-pricing-awareness-market-data.

Added: Order entity persisted in shared runtime database (OrderBook table).
- orderId (string/uuid, primary key)
- accountId (int)
- security (string ticker)
- side (Buy/Sell)
- quantity (int)
- remainingQuantity (int)
- limitPrice (decimal(18,3))
- status (NEW|PARTIALLY_FILLED|FILLED|CANCELED|REJECTED)
- createdAt (timestamp)
- updatedAt (timestamp)
- lastExecutionPrice (decimal(18,3), nullable)
- lastFillQuantity (int, nullable)
Added: in-memory matcher telemetry counters (exported via /metrics) for lifecycle and auto-fill behavior.
Changed: none in existing trade/position schema required by this state (fills remain integrated through current trade/position flow).
Removed: none.

Backward compatibility requirements should be reflected in:
- requirements/functional-delta.md
- requirements/nonfunctional-delta.md
- contracts/contract-delta.md
Open order count semantics:
- open means status in NEW|PARTIALLY_FILLED.
- unfilled means order has remainingQuantity > 0.
- These semantics drive required metrics and dashboard interpretation.
Auto-fill policy semantics:
- Buy order is in-the-money when marketPrice <= limitPrice.
- Sell order is in-the-money when marketPrice >= limitPrice.
- remaining < 1000: full fill, otherwise half fill (rounded up), on each matcher tick.