Bookends v4.0.2

Critical fix for users upgrading from v3.x.

v4.0.0's preset-system migration provisioned "Basic bookends" as a starter preset and — if the user had never used the (new) preset system — set it as the active preset. On next boot, the init-time "re-apply active preset" step would then overwrite the user's customised v3.x layout with Basic bookends' minimal content. Reported on Reddit shortly after release.

v4.0.2's migration now detects a pre-existing v3.x layout (any position with configured lines) and skips the active-preset assignment for those users. Basic bookends still ships as a reference preset in their library — it just doesn't get switched to automatically.

If your layout was already lost on v4.0.0 or v4.0.1, v4.0.2 can't restore it — the damage was written to disk on the first flush after upgrade. Your only recovery path is a pre-v4 backup of koreader/settings/bookends.lua. Apologies.

Clean installs and existing v4.x users are unaffected by this change.