docs: expand AOXCUnity roadmap with refactor guidance and quantum-ready strategy

[aoxc]

Motivation

• Provide a professional, operator-focused answer to whether the existing Unity consensus stack should be deleted and how to evolve it safely.
• Capture higher-level differentiation goals so AOXC can stand out (policy-aware finality, lane-agnostic execution, evidence-first security).
• Add a pragmatic, phased post-quantum preparedness plan so the consensus engine is crypto-agile without risking immediate performance/regression issues.

Description

• Added a new decision section in docs/src/AOXCUNITY_ENGINE_ROADMAP_TR.md that advises against deleting aoxcunity and recommends an orchestrator-centric refactor that preserves primitive modules.
• Introduced three advanced differentiation patterns: constitutional/policy-aware finality, multi-lane (lane-agnostic) consensus separation, and an evidence-first security/evidence lifecycle model.
• Added a realistic post-quantum roadmap (Q1 crypto-agility traits, Q2 hybrid-testnet experiments, Q3 governance-driven mainnet migration) and related technical principles for transition readiness.

Testing

• No automated tests were run because this is a documentation-only change and does not modify runtime code or build artifacts.

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Codex Task