pub fn read_freelist(pager: &Pager, head: u32) -> Result<(Vec<u32>, Vec<u32>)>Expand description
Walks the freelist chain rooted at head and returns every free leaf-page
ID. The trunk pages themselves are not included — they’re live metadata.
Returns the trunk page numbers separately so the caller can release them
(the next save re-encodes the freelist from scratch and frees the old
trunks for reuse).
head == 0 → empty freelist; returns (vec![], vec![]).