* perf(text): keep glyph coverage when layout resizes a text box
Every layout write invalidated a text node's coverage record by id, and the record compared its width and height, so each measurement shaped the text twice. Coverage now ignores the box size unless the text is truncated, and an update that changes only fields coverage compares keeps the record. A demo load went from about 38,000 coverage checks with 228 hits to one shaping per text node.
* perf(editor): skip component sync for layout's own writes
Layout lays out instances itself, and the edit that made it run has already scheduled its sync. Its size and position writes scheduled about 56,000 more, so each yield of an async build re-synchronised components and re-laid out whole pages.
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