bulk
Bulk-download semantics: by default skip already-cached tiles, otherwise force a network fetch and write through to store. Unlike fetchTile, this bypasses isCacheOnly — bulk is a user-initiated "fetch these bytes now" operation orthogonal to the renderer's offline toggle. Returns the blob (cached or freshly fetched), or null when there's no cached tile and no network source / network fetch failed.
Parameters
override
when true, skip the cache read and force a fresh network fetch for every tile (still write-through to store). Used by bulk download's "re-download everything" mode — mirrors pre-refactor makeLocal(overrideCache).