pet.info accepts knownRevision; when it matches the active sheet's
revision the multi-MB spritesheetBase64 is elided and
spritesheetUnchanged=true is returned. The desktop floating pet passes
the revision it already holds and keeps its cached bytes, so backstop
refreshes no longer resend ~3.2MB frames over the WS (write-loop stalls,
disconnect storms). Legacy callers omitting knownRevision get the full
payload unchanged.
Teknium
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