Ports the ~/.cache -> /devl/user-cache redirect pattern (already applied
manually on heimdall) into cf-node-bootstrap's extras/ plugin system, so
it's an optional step for any future node with the same secondary-SSD
layout (heimdall/navi/sif convention: small root + /devl for fast local
storage). Skips cleanly on nodes without a separate /devl mount.
Redirects XDG_CACHE_HOME plus symlinks the hardcoded ~/.cache/{pip,
whisper,clip,huggingface} paths that ignore XDG_CACHE_HOME. Leaves
HF_HOME (curated model store) untouched.
Verified with -D (dry-run) and -i (real) against sif.