feat(risk): add Global ETF research mandate contract

[Pigbibi]

Summary

• add the exact global_etf_rotation_etf_only_research_v1 research-only mandate contract
• enforce max two simulated positions, aggregate 1% completed-session loss-budget sizing, 5% gap-aware per-position stop binding, and strategy/account breakers
• preserve exactly-once RiskEngine.assess() ownership and keep execution_authorized=false

Scope

• src/quant_platform_kit/risk/gate.py
• tests/test_risk_gate.py
• no provider, data, backtest, runtime, config, platform, deploy, paper, shadow, live, order, or capital change

Evidence

• freeze receipt SHA-256: 6c2e404588671fe2829c139bb690e16c061681cfa59b5fe91a5f3477d9068d67
• RED: 41 failed / 4 passed before implementation
• GREEN: targeted 6 passed / 45 subtests; full 938 passed, 1 skipped / 176 subtests
• Ruff, compileall, lock, dependency compatibility, package/install/import, scope, secret, and diff gates passed

[chatgpt-codex-connector]

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