Review found the build fallback could inherit a stale digest pin (compose build aborts), a slash-shaped/non-ghcr lock ref caused a doomed pull, env mode never persisted the pin (host restart used a nonexistent default tag), and the resolver test was unlinted/unrun in CI. Resolver now always leaves a coherent pin, validates ghcr.io/<owner>/<name>@sha256 refs only, exports the mode flag (drops the file-level shellcheck disable), and CI lints + runs the script unit tests.
A checkout path containing shell syntax ($(), quotes) could otherwise inject
code into /usr/local/bin/clusev, which runs as root via 'sudo clusev update'.
Render the path through printf %q into an unquoted assignment; add a test that
a hostile path does not execute injected code.
boban