Document published OpenCrate packages

[AlexiAxAxA]

Summary

• Document the published opencrate facade and five oc-* packages at 0.0.1.
• Replace the outdated unpublished-package instructions with registry and source-path options.
• Refresh export inventory hashes for the already published manifest changes and these documentation changes; remove the inventory's self-hash.

Verification

• A separate Cargo consumer downloaded all six packages from crates.io and passed cargo check with all five facade modules imported.
• python packaging/open-crate/check.py outputs/open-crate/post-release-content-check --content-only returned zero findings on a tracked-file copy.
• git diff --check passed.