Self-serve runs are retired

The legacy self-serve pipeline (the old POST /api/runs path) was decommissioned in the F3.19 cutover. Report generation now runs on the receipt-backed core pipeline, and the public site serves a curated set of pinned reports rather than ad-hoc runs.

Operators: report production is driven by the core run API (POST /api/core/runs), which is authenticated and rate-limited — not exposed as a public form.