Run the kiosk on Chromium, and take the stray media server off musicdolphin

Chromium: same page, same machine, idle, Firefox 24.2% of a core against Chromium's
11.4%. The build comes from archive.raspberrypi.com (a "+rpt" version) and is patched
for this board's V3D GPU; Debian ships a much older chromium, so the archive matters.
The whole userland here is 32-bit armhf on a 64-bit kernel, which Firefox handles worse
than Chromium does. --use-gl=egl, --enable-gpu-rasterization, --ignore-gpu-blocklist
and --enable-zero-copy are what keep rasterization on the GPU: Chromium's blocklist
does not recognise this driver and silently falls back to software without them.
pi_kiosk_browser: firefox still works, as the fallback if an update ever regresses.

Debug mode also gains xdotool, scrot and --remote-debugging-port=9222 (on 127.0.0.1),
because firing XTEST key events at a window lands about half the time and a benchmark
you cannot verify the state of is worse than none.

pi_squeezeserver gains an absent path, and mediapis.yml derives its state from
mediapi_has_squeezeserver, which defaults to false for the whole group. false means
"actively remove", not "skip": musicdolphin has been running a Logitech Media Server
that no playbook installs and nothing talks to - every squeezelite in the fleet points
at pi_squeezelite_squeezeserver (192.168.178.80, the server) - while costing ~30 MB
resident and ~47 MB of swap on a 2 GB Pi that also drives the kiosk. The absent path
stops it, purges the package, unregisters it from sysdweb, drops the port 80 -> 9000
redirect and deletes its database and logs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

roles/pi_kiosk/defaults/main.yml

@@ -2,8 +2,15 @@
 pi_kiosk_user: "kiosk"
 pi_kiosk_url: "http://localhost:8080"
 
+# "chromium" - the build from archive.raspberrypi.com (versions carry a "+rpt" suffix),
+#              which Raspberry Pi patch for this board's V3D GPU. Faster than Firefox
+#              here by a wide margin; see the README.
+# "firefox"   - firefox-esr from Debian. Kept switchable because it was the original
+#              kiosk browser and is the fallback if a Chromium update ever regresses.
+pi_kiosk_browser: "chromium"
+
 # "kiosk" - the page full-screen with no browser chrome and no pointer. The normal mode.
-# "debug" - the same page in an ordinary Firefox window, pointer visible, with an
+# "debug" - the same page in an ordinary browser window, pointer visible, with an
 #           Openbox root menu (right-click the desktop) offering a terminal, so the
 #           device can be poked at on its own screen. Switch back with
 #           `just run mediapis.yml musicdolphin -e pi_kiosk_mode=kiosk`, or by editing