libkungfu developer site disaster recovery

This is the stable incident entry for libkungfu.org. It is intentionally discoverable, but the mirrored developer pages remain non-canonical copies of the corresponding libkungfu.dev surfaces.

1. Confirm the primary site is unavailable from more than one network.
2. Check mirror status and its SHA-256 sidecar.
3. Use this mirror for read-only documentation and downloads only; each primary URL remains canonical.
4. Do not publish, qualify, or infer production health from mirror availability.
5. When the primary recovers, return readers to https://libkungfu.dev/.

This mirror is promoted only from a Buildchain production passport and the exact artifact from the same successful workflow run.