PERF.23 Scale: cc-ifc copies the file for the worker and keeps every mesh in memory; save is O(lines) (extends PERF.8, PERF.10)

Measured: the index scans 1.9 GB in 15.9 s and 3.3 GB in Node (linear, typed arrays, lazy per-line parse: the healthy template for the other readers). But open-async.js:33 data.slice() doubles the bytes on the page (ceiling about 1 GB in a tab), open plus geometry plus save holds 12.8 times the file (2.57 GB at 200 MB; in the browser the heap grows about 1 GB per 100 MB of IFC: 210 MB peaked at 1.99 GB, 1 GB would need 10 GB), and save() walks every line with three chunks each (model.js:232-256, 8.8 s at 115 MB). Change: transfer the caller's buffer or let the worker read from the Blob; stream meshes to GPU buffers with an LRU instead of keeping all triangles in JS; save by coalesced byte ranges into a writable stream. Pairs with the BimCraft geometry-off-the-page-thread row (PERF.8).