Windows (deckcraft.wxs) and Linux (the desktop file) already offer DeckCraft for .deckcraft,
.pptx, .potx and .ppsx; the macOS Info.plist now declares the same four, so a template or a
slide show opens from Finder as well. A test in apps/deckcraft reads the three packaging files
and fails when they drift apart, and checks every document type names its content type (Finder's
"Change All" needs it). Progress log row for #138 and #347.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
