Populate message_count for an existing thread list.
This is used by the /threads modal to render rows quickly, then backfill
counts in the background without issuing a second thread-list query.
populate_thread_message_counts(
threads: list[ThreadInfo],
) -> list[ThreadInfo]| Name | Type | Description |
|---|---|---|
threads* | list[ThreadInfo] | Thread rows to enrich in place. |