The cache lived inline in vite.config.ts, and the renderer builder tests use a bare fixture
config, so nothing exercised it: a broken warm path would still pass every test.
Move it to scripts/compiler-cache.mjs (behaviour unchanged; toolchain files and cache root are
now parameters, and an existing closeBundle hook is chained instead of replaced) and test hit
vs fresh output, toolchain/NODE_ENV generations, corrupt entries, pruning, incremental (watch)
rebuilds and the dev-server bypass. A cold and warm production build of the real app stay
byte-identical. Reported by Greptile on #135092.
d2cbfcf7db