Plan 3D migration architecture

[Hartwich]

Goal

Create a technical plan for migrating Drift Racer to a 3D host view.

Codex Auftrag

Plan first; do not rewrite the game yet.

Focus

• current 2D structure
• recommended 3D rendering approach
• required game-state changes
• required asset/model placeholders
• risks and incremental migration steps

Acceptance Criteria

• Add a short markdown document under docs/ or the repo README.
• Identify which files need to change in later implementation issues.
• Do not rewrite the game yet.
• npm run typecheck passes if code is touched.

Safety

Do not add copyrighted, unclear, or unreviewed third-party assets or content.