A packaged desktop app launches to a blank page with a bare
ERR_FILE_NOT_FOUND when dist/index.html isn't in the bundle (#39484).
This happens when the build step fails (e.g. a stale checkout that
fails typecheck) but electron-builder packages anyway, shipping an
empty dist/.
- build-time: scripts/assert-dist-built.cjs runs at the tail of the
`build` script and aborts before electron-builder if dist/index.html
or the vite JS bundle is missing/empty. Every packaging path
(pack, dist*) inherits it via `npm run build &&`.
- runtime: resolveRendererIndex() now logs a clear 'packaged without a
renderer bundle — rebuild with hermes desktop --force-build' message
when no index.html exists, instead of silently loading a missing path.
- runtime: resolveWebDist() logs when it falls back to an asar-internal
dist that isn't a real directory (the dashboard 404 class, #41327/#39472),
rather than returning an unservable path silently.
Adds scripts/assert-dist-built.test.cjs (node:test) covering the guard.
