Cloud/remote-session file sync gets cryptographic tamper verification

Claude Code adds a large set of new functions that verify git commits, trees, and objects built for syncing files during cloud or remote sessions read back as exactly what their content hashes claim. If they don't match, sync now reports a distinct "tampered" status instead of silently proceeding. Before uploading working-tree state, this process also builds a scratch index and tree that filters out uncommitted files that look like credentials, such as .env, .npmrc, .pem files, SSH keys, and AWS, Azure, GnuPG, or Kubernetes config files.