PERF.52 Apps: the add-on loader is serial and imports every add-on's help at activation: 13 add-ons on = 235 requests, 3.0 MB, 2.5 s of steps

addons.js (the shell copy synced into every build) awaits each bundled addon.json in turn (:390-396; 13 in CadCraft, default-off ones too), activates one after another (:381) and imports each add-on's help module at activation (:572-589; Electrical's 58 KB every start). Measured with 13 add-ons on (tools/perf/addons-load.mjs): 235 requests, 3.0 MB, 2,552 ms of serial steps, longest step 382 ms; in parallel the same work is about 0.4 s. Baseline CadCraft with nothing on: 13 serial addon.json round trips, about 0.9 s on a real line. Change: put every bundled manifest into addons/index.json at release time (one request) or Promise.all the discovery, import all entries in parallel and activate() in index order, import help lazily from api.help on F1.