The build deletes it. vite clears outDir (emptyOutDir: true), and that file is
the only reason //go:embed all:dist compiles in a fresh clone - without it a
clone that has not run a frontend build cannot run go build at all.
Found because it happened: a pnpm build during the transcode work removed the
tracked file, and it showed up as a deletion waiting to be committed. A
developer who ran a build and then staged everything would have broken every
clone silently, and the symptom would appear on someone else's machine.
The build now regenerates it, with the explanation in the file itself so the
next person to see it knows what it is for.
