Preserve the root repository landing page

[offalexjackson777-stack]

What changed

• removes .github/README.md, which GitHub renders ahead of the root README on the repository homepage
• removes that file from the canonical Atlas projection
• adds a regression contract that forbids recreating the landing-page override
• regenerates the affected ownership projections

Why

The ordinary-visitor inspection showed the public homepage rendering “GitHub Automation” instead of the HyperFlux Next front door. GitHub's README precedence made the generated .github/README.md override the intended root README.md.

Verification

• focused repository-experience and Atlas contracts: 16 passed
• exact pinned fast lane: 25 of 25 nodes passed on e4c51fb
• generated freshness and all tracked Markdown link/anchor checks passed

No release, tag, package publication, hardware-writing authorization, or publication claim is included.