Build the read-side navigation index for a vault. mtime-incremental: each
article is parsed at most once per (path, mtime), so a rebuild after touching
one file re-parses ONLY that file. Deterministic: stems are visited in sorted
order and every map array is sorted, so two builds of the same vault produce
byte-identical maps. Makes ZERO embedding calls.
Build the read-side navigation index for a vault. mtime-incremental: each article is parsed at most once per (path, mtime), so a rebuild after touching one file re-parses ONLY that file. Deterministic: stems are visited in sorted order and every map array is sorted, so two builds of the same vault produce byte-identical maps. Makes ZERO embedding calls.