Add production safety foundations and policy coverage

[Sunny-commit]

Summary

Move OpenDecision from a minimal typed-decision wrapper toward an auditable control-layer foundation while preserving its pre-1.0, non-guarantee positioning.

Closes part of #4 and #6.

Added

• strict decision-contract and provider-output validation
• deterministic rule provider and ordered provider fallback chains
• configurable raise/review/block failure behavior
• decision IDs, timestamps, policy metadata, context hashes, and provider-attempt telemetry
• privacy-preserving memory and JSONL audit sinks
• human-review lifecycle with repeated-loop protection
• versioned/inheritable YAML policies with v0.1 compatibility
• accuracy, confusion, and Brier-score evaluation primitives
• policy packs for data access, payments, HR/permissions, external APIs, destructive commands, and privacy exposure
• production-readiness guidance, risk matrix, deployment checklist, and changelog
• coverage, Ruff, strict mypy, and Python 3.10–3.13 CI gates

Important limitations

This remains a control-layer library, not a complete security boundary. The in-memory review store is not production storage. Applications still need authentication, authorization, durable review infrastructure, encryption, retention, monitoring, calibration, and enforcement at the protected tool boundary.

Validation

• 24 tests passed
• 87% branch-aware coverage (85% gate)
• Ruff passed
• strict mypy passed
• compileall passed
• GitHub Actions passed on Python 3.10, 3.11, 3.12, and 3.13

The PR remains draft for maintainer review and must not be merged without explicit approval.