Protect shared setup, compilation, artifact copy, and target cleanup with
one flock lock per checkout. Route watch builds and frontend cleanup
through the protected scripts.
Document the lock contract and normalize the frontend and exporter
build:wasm commands.
Closes#11901
AI-assisted-by: Space Bunny Free
* ✨ Add headless wasm render backend to the exporter
* ♻️ Move render-wasm bridge to common and split wasm builds
* 🔧 Upload builtin font variants in the wasm exporter
* ♻️ Move shared font and resources utils out of render_wasm
* ⚡ Fetch only the exported roots in the wasm exporter
* ⚡ Bound save_layer rects in the vector export path
