PERF.22 Scale: cc-dwg keeps 35 bytes of heap per file byte, clones the drawing out of the worker, and the writer is super-linear (extends PERF.5, PERF.9, PERF.10)

Measured at 10x (a 76 MB R2004 drawing, 1.4 M entities): readDwg 19.9 s and 2.6 GB after read (one object per entity and per vertex, objects-read.js:608-613 and :1105), the worker reply structuredClone adds 1.06 GB and 14.6 s (read-async.js:67), writeDwg 66 s (33 s from a fresh model), exponent 1.3. A 760 MB drawing would need about 27 GB: it does not fit anywhere. Browser ceiling today about 55 to 110 MB. Change: a struct-of-arrays entity store with lazy per-entity decode from the object map (the map and section locators are small; readDwg(bytes) at read.js:30 becomes openDwg(blob) with byte-range decoding), the worker reply as transferable typed buffers (or decode on the page from the transferred bytes), and a writer that streams sections to a FileSystemWritableFileStream. Reader L, writer M. The four apps carry byte copies of lib/dwg.