Build script now tries trunk first (local dev), then falls back to
ui/prebuilt.html (cargo install path). Publish CI installs trunk and
wasm32 target, runs cargo check to generate ui/prebuilt.html, then
publishes with --allow-dirty so crates.io bundle includes the built UI.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>