Operator chose option A. Opening hydrates; a consumer that wants a fresh store
removes the records it does not keep, upserts, and flushes, and the atomic
snapshot replace does the rest. No CultLib API is added and PullOnOpen goes in
Cut 3. The two AquaSynth single-document writers adopt that form; the
File.Exists-style setters in AquaSynth and Mimir just drop the property.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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