docs: roadmap expansion for procedural and systems suite

[f-gueguen]

Summary

• add Milestone 0.4 roadmap covering procedural generators and complete gameplay systems (WFC, dungeon suites, L-systems, diamond-square, maze pack, game loop, camera, particles, etc.)
• surface planned expansions in README snapshot and quick-nav docs (index.d.ts, index2.d.ts, project.md)
• provide LLM-oriented references to examples/tests for quick algorithm selection

Testing

• npm run lint