iso: fix packages.x86_64 (no inline comments; gstreamer-vaapi -> gst-plugin-va)

Inline comments after a package name broke kitty/flatpak (became invalid
names with trailing whitespace). gstreamer-vaapi was removed from Arch.
calamares is AUR-only -> commented pending a [tanin] rebuild decision.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

iso/build-profile/syslinux/syslinux.cfg

@@ -0,0 +1,11 @@
+DEFAULT select
+
+LABEL select
+COM32 whichsys.c32
+APPEND -pxe- pxe -sys- sys -iso- sys
+
+LABEL pxe
+CONFIG archiso_pxe.cfg
+
+LABEL sys
+CONFIG archiso_sys.cfg