The seen map was keyed by the full ArtworkID, which embeds the client token's
LastUpdate: every scan bump rotated the key, so the same-bytes dedup (and its
cheap version re-persist path) never fired in production and stale entries
accumulated forever. The key now zeroes LastUpdate, making the map bounded by
entity count and restoring the tested dedup behavior.
Cleanups from the same review: the base83 encoder is now exported from the
blurhash package and the DTO's duplicate copy is deleted; the always-set
blurHashes field lost its test-shaped nil guards; clearIfStored dropped its
inert version parameter (cleared rows never have their timestamp read); the
teeReader done flag is replaced by nilling the callback; worker-era comments
(async, cache-miss recompute) were updated to the inline design; and the e2e
specs assert directly instead of polling, since the hash is persisted before
the read helpers return.
The tee was built around io.NopCloser(r) and teeCachedStream.Close only closed the
tee, so the underlying CachedStream (an open cache-file fd, or the raw source stream
when the image cache is disabled) was never closed — one fd leaked per teed serve,
enough to exhaust the process limit during a client's initial cover sync. The tee now
wraps the stream directly and its Close propagates; teeCachedStream is gone (all
artwork handlers io.Copy, none Seek). The file is renamed to tee_reader.go since the
wrapper is generic, not blurhash-specific.
