WIP: Initial formalizations for Polignac, Tijdeman, and Green-Tao conjectures

Hi! I am working on the initial formalizations for the following topics and will submit a Pull Request shortly:

* Polignac's conjecture (consecutive prime gaps)[cite: 1]
* Tijdeman's theorem[cite: 2]
* Green–Tao theorem[cite: 3]

Opening this issue as a WIP to coordinate and avoid duplicated efforts.

This WIP issue covers initial formalizations of Polignac's conjecture, Tijdeman's theorem, and the Green–Tao theorem. Review the existing formal-conjectures collection and coordinate with the author before starting, since a pull request is expected shortly; done means the three stated topics are formalized and submitted without duplicated effort.

Written by the indexing model from the issue text.