fix(readiness): declare GitHub API versions surface

[auscaster]

Summary

• declare GitHub's public GET /versions endpoint as the machine-readable supported-version descriptor for the GitHub REST API
• bind the exact first-party documentation and graph relation to the existing repository-operations assessment
• exercise the ordinary one-vendor Agent Readiness maintenance path against live release sha256:d1cb219c8f6be3606007166b616e13fb46fee27507930122f428f1d5487097e1

Evidence

GitHub documents GET https://api.github.com/versions as the endpoint returning all currently supported REST API versions. The endpoint currently returns 2026-03-10 and 2022-11-28.

• https://docs.github.com/en/rest/meta/meta?apiVersion=2026-03-10
• https://api.github.com/versions

Local proof

• complete declaration tree: 20 vendors / 22 declarations
• exact changed closure: 1 vendor / 1 declaration
• Catalog contract suite: 404 passed
• DCO sign-off present

The declaration contains no readiness result or grade. Evidence Operations remains the sole factual-assessment lane.