Agent Skills Manifest

S20-B2 — agent-skills manifest (pay.sh v1.0 compatible).

Behind feature flag GECKO_MANIFEST_PUBLIC (default false). When the flag is unset/false, returns 503 + X-Gecko-Manifest-Status: draft so pay.sh’s crawler can’t pick up DRAFT copy. Flip the env to true once business-manager + product-designer sign off on the 12 description strings (per memory project_output_layer_positioning).