Stop installing ffmpeg over ffmpeg-free, which a fresh machine refuses

A clean Fedora Workstation ships ffmpeg-free, and desktop-packages listed
ffmpeg (RPM Fusion). Those two conflict rather than add: dnf will not erase
the preinstalled ffmpeg-free to make room, so the WHOLE desktop transaction
failed to resolve and no desktop package installed. The codec section already
does the trade correctly -- `dnf swap ffmpeg-free ffmpeg --allowerasing` --
so ffmpeg simply does not belong in the eager list. A machine that already
had ffmpeg (every one this repo was ever run on) sailed past this; the first
genuinely fresh Workstation install is what surfaced it.

Also: report_missing false-warned that awk was unavailable. rpm -q
--whatprovides matches a package's named provides, but awk is provided as the
file path /usr/bin/awk (by gawk), which that query misses. Fall back to
command -v so a capability provided by path is not reported as missing.

Found by a fresh-VM certification run, which is exactly the failure mode a
re-run on an already-configured machine cannot reproduce.

Claude-Session: https://claude.ai/code/session_01Epx9ZC1gwm81K3jm9x9CKh

setup/packages/desktop-packages

@@ -8,7 +8,12 @@ decibels
 espanso-wayland
 desktop-file-utils
 dnf-plugins-core
-ffmpeg
+# ffmpeg is deliberately NOT here: Fedora ships ffmpeg-free, and installing
+# RPM Fusion's ffmpeg over it is a CONFLICT, not an addition -- dnf refuses
+# the whole transaction rather than erase the preinstalled one. The codec
+# section swaps ffmpeg-free -> ffmpeg with --allowerasing, which is the only
+# correct way to make that trade. A fresh Workstation install found this; a
+# machine that already had ffmpeg never would.
 firamono-nerd-fonts
 # A second engine to check pages against; Helium is the daily driver. Its
 # chrome is themed from config/firefox, which link-dotfiles places into the