Returns the most recent messages for up to 50 chats in a single request for the specified creator, keyed by the input chat UUID (the counterpart user UUID).

This is the bulk counterpart to GET /creators/{creatorUserUuid}/chats/{userUuid}/messages. Per-key errors are reported inside the 200 response body so a single unreachable chat never collapses the whole request.

<Note>Maximum 50 chat UUIDs per request. Failed keys are reported as { "error": "not_found" }.</Note>

<Note>Read-only: fetching messages in bulk does not mutate read state — messages are not marked read and isRead reflects each message's state at read time.</Note>

<Note>Direct messages only. Mass (broadcast) messages are excluded from this endpoint. The per-chat listing endpoints include them interleaved with the 1:1 thread, so the two surfaces legitimately return different messages for the same chat — a message present in a chat listing can be absent here without anything being lost. List broadcasts separately via GET /creators/{creatorUserUuid}/chats/mass-messages.</Note>

<Note>Rate-limit cost. Each request consumes one rate-limit point per 10 chat UUIDs, rounded up: 1-10 chats cost 1 point, 50 chats cost 5.</Note>