Release v0.2.2 with streamlined public documentation

[JROChub]

Summary

• delete docs/research_claim.md and remove every reference to it
• remove the disclaimer and adjacent caveat paragraphs from the crates.io README introduction
• update the observatory link to the technical security model
• synchronize crate, lockfile, protocol guide, verification guide, site label, and release notes at v0.2.2

Clean package verification

• committed before packaging
• git status --porcelain=v1 returned no output
• cargo package --locked passed without --allow-dirty
• cargo publish --dry-run --locked passed without --allow-dirty
• inspected target/package/power_house-0.2.2.crate; deleted document is absent and the corrected README is present

Validation

• cargo fmt --check
• cargo clippy --all-targets --all-features --locked -- -D warnings
• cargo test --all-targets --locked (42 + 6 tests)
• cargo test --all-targets --features net --locked (57 + 6 tests)
• python3 scripts/test_sparse_verifier.py