Each original's save path is now
YYYY/YYYY-MM/YYYY-MM-DD/YYYY-MM-DD.<fileID><ext> under the library's
download directory, dated by takenAt in the machine's time zone. The
directory defaults to photos/ in the working directory, resolved once at
open. savePath is always a string, with or without a content cache, and
isLocal is true only when the original is there.
photo.download() puts the original at its save path: copied from the
cache when the cache holds it, fetched straight there otherwise.
lib.backup() uses the same code for each file, writes each file's JSON
beside it, and links collections/ to the save paths. The backup has no
originals/ folder.
Model: opus-5-5
Bounds the originals cache and evicts least-recently-used. cacheOriginalsMaxBytes default 100 GiB; the effective limit adapts down via fs.statfs to keep freeBelowBytes (default 50 GiB) free. Over-limit writes evict unpinned originals oldest-mtime-first (mtime touched on read); pinned files (favorites + latest week) are skipped and an over-budget on-demand fetch proceeds over-limit. Every in-flight write is excluded from eviction, so concurrent fetches never delete each other's just-stored file. Only cacheDirectory/originals is evicted; downloadDirectory and thumbnails never.
Model: opus-4-8