content(blog): the Turing Checkmate — decidability implies a decider (our answer to 'where is free will hiding')

This is a live, recomputable drift receipt — the on-chip proof of where this commit's work landed (in its authorized domain, out of it, or unplaced), sealed with a signature anyone can verify. It is the same receipt shipped in the on-commit email, hosted here so the claim is checkable on the open web. The full receipt (attestation, density panel, full commit message) publishes at /commit/3b2b6e7b6/ shortly after the commit lands.