Implement mirror-aware sizing and production risk limits

[carndog]

Outcome

Calculate live order size from explicit portfolio allocation and the Agent Portfolio virtual/real relationship while enforcing the exact revision-controlled production risk policy and objective configuration.

Acceptance criteria

• Define the source of virtual balance, real allocation, mirror ratio and available capacity
• Resolve and record the PortfolioRiskPolicy revision effective at the production decision instant
• Resolve and record the PerformanceObjectiveSchedule revision and objective period effective at that instant
• Use an immutable, freshness-validated portfolio-performance snapshot
• Apply maximum order size, instrument exposure, portfolio exposure, daily-loss and return-protection limits
• Include open orders and reserved pending exposure in available-capacity calculations
• Create the approved exposure reservation atomically so concurrent decisions cannot oversubscribe capacity
• Never increase the strategy's requested exposure, invent a trade or reverse its direction
• Preserve genuinely risk-reducing actions when new risk is restricted
• Handle stale or unavailable balance, valuation, policy, objective or allocation data by rejecting execution
• Apply precision, minimum-order and rounding rules explicitly
• Persist requested and approved sizing, all three revision references, objective period, performance snapshot, evaluator code version and rejection reasons
• Require policy limits and objectives to be configured independently for Real execution
• Keep real thresholds, objectives and portfolio values out of the public repository and logs
• Prove behaviour through deterministic unit, concurrency and scenario tests
• Default to no live allocation

Dependencies

• RiskGate pipeline: Implement RiskGate and the end-to-end stubbed OrderExecutor pipeline #16
• PortfolioRiskPolicy revisions: Define the revision-controlled PortfolioRiskPolicy domain and XML contract #49 and Persist and administer PortfolioRiskPolicy revisions #52
• PerformanceObjectiveSchedule revisions: Define revision-controlled PerformanceObjectiveSchedule semantics and XML #51 and Persist and administer PerformanceObjectiveSchedule revisions #50
• Portfolio-performance snapshots: Build auditable portfolio performance snapshots for RiskGate #53