Roadmap: v0.2 language subset scope

[JROChub]

Context

• We have ROC_VISION.md and SPEC.md, but no concrete v0.2 scope for contributors.

Goal

• Define a focused v0.2 subset and priorities for contributors to align on.

Proposal

• Add a short Roadmap section (or docs/ROADMAP.md) with in-scope and out-of-scope items.
• Include priorities and rationale so volunteers can pick work that matches the vision.

Acceptance criteria

• v0.2 scope list with 5-10 items covering language, tooling, and docs.
• Explicit non-goals list.
• Links to ROC_VISION.md and SPEC.md.