Tree shake unused client reference exports

[hi-ogawa]

Just remembered we haven't taken care of this while checking mantine example build in hi-ogawa/next-app-template#1

Probably ssr build creates one giant client reference which holds entire @mantine/core

▶▶▶ REACT SERVER BUILD (ssr) [4/4]
vite v5.3.4 building SSR bundle for production...
✓ 656 modules transformed.
dist/server/.vite/manifest.json                                       3.24 kB
dist/server/assets/create-theme-BnhyR2hf.js                           0.08 kB
dist/server/assets/_virtual_server-references-y-E-dViC-y-E-dViC.js    0.09 kB
dist/server/assets/theme-C6QRzPcV.js                                  0.16 kB
dist/server/assets/_virtual_client-references-gr0n_QHF.js             0.31 kB
dist/server/assets/_virtual_ssr-assets-CXKxdVsi.js                    0.38 kB
dist/server/assets/ColorSchemeToggle-sj0jnDtg.js                      0.68 kB
dist/server/assets/client-BQ8swztY-CtCsvDgM.js                        0.71 kB
dist/server/assets/_virtual_route-manifest-DMuu4Nf6.js                1.00 kB
dist/server/assets/client-2vuMQ-3j.js                                 3.77 kB
dist/server/index.js                                                 28.29 kB
dist/server/assets/Button-Jhh0NtFR.js                                72.04 kB
dist/server/assets/index-DPfROtXM.js                                342.41 kB
dist/server/assets/index-BjaqkVyi.js                                552.97 kB      // <-- this one

// dist/server/assets/_virtual_client-references-gr0n_QHF.js
const _virtual_clientReferences = {
  "cbf0dc6ca9": () => import("./client-2vuMQ-3j.js"),
  "cff744f2a7": () => import("./index-BjaqkVyi.js"),  // <-- this one
  "0f20e3f653": () => import("./theme-C6QRzPcV.js"),
  "2090238440": () => import("./ColorSchemeToggle-sj0jnDtg.js")
};
export {
  _virtual_clientReferences as default
};

[hi-ogawa]

I wonder how Astro handles for client island. cf. #597