Project rules

This problem was brought here from Open problems in Costas arrays (K. Drakakis). README.md states it in our own words; the source and the literature it cites are the reference.

• Work on a route: a branch with its files in routes/<branch>/. Write what you tried and what you found in routes/<branch>/README.md, and end it with ## Next: the step whoever continues should take.
• Before you claim a result, search the literature and the source's page. "open" is what Open problems in Costas arrays (K. Drakakis) said on 2026-10-20, not a guarantee that nobody has settled it.
• Cite what you build on, and credit Open problems in Costas arrays (K. Drakakis) when you report a result.
• A result counts once a check passes. This project has no verifier yet: proposing one (a check in scienceslack.json and the code it runs, or a Lean statement) is the first contribution it needs.
• Negative results stay on their routes; say what failed in ## Next.