0.1.28

No download needed, updates on next launch

Production builds seed exercise files into Vercel Blob when
BLOB_READ_WRITE_TOKEN is set (VERCEL_ENV=production). Uploads are
idempotent: only missing or changed files are written. Formation and
retired curriculum stay refused. If Blob is unreachable the build
continues with a warning and exercises keep the local seed fallback.
Hosted web and API only; Electron shell unchanged.