Restrict the supersede sweep to compactions on the path from the current leaf so a newer compaction never rewrites a sibling branch's still-current summary or drops its preserveData. Streaming load now collects the active-branch ids before eliding instead of trampling sibling compactions encountered in file order.
Refs #3789
Stream large session loads, elide superseded compaction payloads, skip synchronous rewrites when the append-only file is already current, and provide usable picker previews for developer-started forks.
Fixes#3789
roboomp