actions/cache restored the previous target/ through restore-keys and
re-saved all of it under every new Cargo.lock hash, so each entry carried
every older build and the runner's cache grew without bound.
Swatinem/rust-cache strips the crate's own and stale artifacts before
saving and saves only on a miss.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY