Beta is now a real stabilization branch: publishes on every push to
`beta` (mirroring dev's model, auto-versioned X.Y.Z-beta.<ts>+<sha>,
base version from the latest published tag) instead of a manual
beta-v* tag. Fixes made during the freeze land via fix/<issue> branches
merged into `beta` directly. The gen-index.sh clone for beta pulls
bread-ecosystem's default branch (main) rather than pinning to dev,
since beta is the more stable track and main now carries the
TRACK-aware script.
The fixed /tmp/bread-ecosystem-ci path races when multiple repos' dev/beta
workflows run close together on the same self-hosted runner — one job's
rm -rf/clone can stomp another's in-progress checkout, causing the
regenerate-index step to fail intermittently. Switch to mktemp -d.
Adds dev-release.yml (publishes on every push to dev) and beta-release.yml
(publishes on a beta-v* tag), mirroring the pattern landing in
bread-ecosystem/bread. See bread-ecosystem/docs/release-channels.md for
the three-track policy.
