Roadmap Tier 5 (2026 frontier) — moved

Consolidated into docs/PLAN.md §3 Tier 5.

Roadmap Tier 5 — 2026 frontier

Absorbed into the master plan §3 Tier 5. Five research-flavoured items: reasoning training, test-time compute scaling, vision-language toy, diffusion LM, real sparse MoE kernels. All still ⬜.