Global place ids referenced by this chunk, indexed 0..P-1.
Stored Morton codes, chunk-local, strictly increasing. Typed arrays
rather than plain ones for this and the other per-record fields: a
big chunk holds over a million records, and parsing and holding them
as boxed JS arrays costs several times as much. 32 bits, as every
code is below 4^MAX_SUPPORTED_DEPTH.
Each record's depth in the chunk's quadtree, 0 to max_depth.
Local palette index per record: 0 = "no place", k = palette[k-1].
As wide as the file stores them (Section 8.3's S), rounding 3 bytes
up to a Uint32Array.
One chunk's records (Section 8), decoded: record
jis the cellcodes[j]at depthdepths[j], attributed topalette[paletteIndices[j] - 1](or to no place for index 0).