v0.3.0

First tagged release of cas — npm supply-chain hardening for AWS CodeArtifact.

Initial commands:

• cas drift — fail when package.json and package-lock.json disagree
• cas sri patch / cas sri verify — backfill and verify the SRI integrity hashes CodeArtifact strips from package-lock.json
• cas registry — gate the lockfile against an allowlist of registry hosts
• cas scripts — fail on packages that ship preinstall / install / postinstall scripts

Adds the severity ladder (CRITICAL / HIGH / MEDIUM / LOW / INFO) and a stable --json output schema across every command.