docs: divide research roadmap into layer bands

[NoctilumeDev]

Summary

• define R0 as the boundary-freeze stage rather than an implementation milestone
• group R1-R7 into deterministic foundation, untrusted policy, and continuity/scale bands
• require one-way, versioned handoffs and explicit revalidation for cross-band changes
• clarify that layered design does not imply one microservice per concept

Evidence

ode scripts/verify-repository.mjs

• git diff --check

Scope

Documentation only. The R naming, planned evidence state, and existing R0-R7 stage contents remain intact.