needs_full_build() decided the fast path was safe by hashing only config
inputs (VERSIONS, package lists, hooks, archives, auto/config, Dockerfile).
It never hashed the build logic itself, so a change to build.sh or
lib/fast-path.sh counted as a "light" file and the next build silently
reused a squashfs produced by the old code. The merged-usr /lib fix in the
previous commit only forced a full rebuild by accident (the overlay
manifest saw firmware move from lib/ to usr/lib/).
hash_heavy_config now covers every *.sh under iso/builder (build.sh, the
build-*.sh helpers, lib/*.sh) plus auto/. A change to build logic is now
as heavy as a package-list change. config/bootloaders stays excluded (the
fast path regenerates the outer ISO layer from it every time). Hash is
deterministic (LC_ALL=C sort).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01H2LLuid8PFhBqBPcxXxkQU
