Upgrade Vault TLS dependencies and GitHub release workflow

[chriswiggins]

• Upgrade vaultrs, vaultrs-login, and rustify; bump the package to 0.3.0 and remove the unused vendored OpenSSL dependency.
• Cover VAULT_SKIP_VERIFY behavior and document system trust stores and private CA configuration for macOS and WSL.
• Refresh CI and the GitHub release workflow to build five platform archives with checksums using supported runners and actions.
• The legacy Docker-backed integration test is incompatible with Docker 29, so release verification runs the unit suite while that harness remains unresolved.