vendor: serve the modules as .js — nginx does not map .mjs

Deployed and immediately broken: stock nginx mime.types has no .mjs entry, so preact.mjs and htm.mjs went out as application/octet-stream and every browser refused them.

• Renaming to .js fixes it with no server config: .js is mapped to text/javascript on every host, so this cannot regress on a reinstall, a new box, or the second site served off this same tree.

• This is the same failure the probe harness hit before it learned .mjs, which is the one place .mjs still needs to work: the harness serves the tree itself.

▶ Play it: Neon Fiscal Year → Benthic Patience → Silken Reentry — a constellation across three families — the path is the mix https://stellate.app/?genre=citypop&seed=8524&path=1530.6221,586.10667,1376.19565&xdur=0.056

63cdc83 https://github.com/aboard-io/stellate/commit/63cdc83ca28430f172fefeeab0c67d8a3ac410b6