PERF.57 Apps: start-up work for panels nobody opened: BimCraft massing 191 ms, ModelCraft swatches 182 ms plus 650 ms idle tasks, CivilCraft plants seed, exr table

BimCraft massingOptions() runs 191 ms inside mountProgram (design-ui.js:77); ModelCraft paints a swatch per library material from 128 px procedural textures at start (modelcraft.js:557, :581; 182 ms) and is the only app with long tasks during idle (650 ms); CivilCraft fetches and cleans plants-seed.json (198 KB) at start (landscape-ui.js:117); exr/util.js builds a 65,536-entry half-float table at import (exr/util.js:38-46); three.module.js top level is 65 to 94 ms. Change: compute on first open of the panel or first paint of the palette (IntersectionObserver or the tab event), fetch plants on first Landscape use, build the half-float table lazily. 0.2 to 0.4 s of blocking per start in the 3D apps.