drazzy.com (ATTinyCore index host) has had an expired TLS certificate
since 2026-06-22 and now 301-redirects http to https, defeating the
plain-http URL pinned to sidestep its TLS issues. Two failure modes:
1. A /root/.arduino15 volume from an older image can reference the index
in config while lacking the file; arduino-cli then fails instance
init outright, breaking EVERY compile, not just ATtiny (issue #254).
2. backend/Dockerfile chained update-index with &&, so any uncached
image build fails hard while the host is broken (exit 1 verified).
A stale index is harmless (ATTinyCore 1.4.1's platform archive and its
micronucleus 2.0a4 both download from github.com); a missing one is
fatal. So: vendor the index under backend/board-indexes/, copy it to
/opt/arduino15-seed in Dockerfile.standalone, and teach entrypoint.sh
to seed any missing package_*.json into /root/.arduino15 at boot,
healing stale volumes. backend/Dockerfile seeds the index directly and
makes update-index best-effort; core install lines stay strict.
Verified: removing the index reproduces the reporter's exact
'Error initializing instance' brick; after seeding, instance init
exits 0 with the host still broken.
a2df942d74