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/templates/openbox-menu.xml.j2

@@ -13,12 +13,12 @@
     <separator/>
     <item label="Open the MusicMouse page">
       <action name="Execute">
-        <command>firefox {{ pi_kiosk_url }}</command>
+        <command>{{ pi_kiosk_browser_command }} {{ pi_kiosk_url }}</command>
       </action>
     </item>
     <item label="Open it full-screen (kiosk)">
       <action name="Execute">
-        <command>firefox --kiosk {{ pi_kiosk_url }}</command>
+        <command>{{ pi_kiosk_browser_command }} --kiosk {{ pi_kiosk_url }}</command>
       </action>
     </item>
     <separator/>

roles/pi_kiosk/templates/xinitrc.j2

@@ -3,21 +3,52 @@
 #
 # Openbox is here for one concrete reason: a browser asks to be full-screen over EWMH,
 # and only a window manager answers that request. With no WM running, --kiosk was
-# silently ignored and Firefox fell back to its default 1280x972 window on a 1920x1080
-# screen - the page in the top-left corner with black bands down the right edge and
-# along the bottom. Openbox costs a couple of MB and does nothing else here.
+# silently ignored and the browser fell back to its default window size in the
+# top-left corner of a 1920x1080 screen - black bands down the right edge and along
+# the bottom, looking exactly like an overscan problem and not being one.
 
 xset s off
 xset -dpms
 xset s noblank
 
+{% if pi_kiosk_browser == 'chromium' %}
+BROWSER=chromium
+
+# The first four flags are the difference between compositing on the GPU and
+# rasterizing every frame on the CPU:
+#   --use-gl=egl                 reach V3D through EGL rather than desktop GLX
+#   --enable-gpu-rasterization   rasterize layer content on the GPU
+#   --ignore-gpu-blocklist       Chromium's blocklist does not know this driver, and
+#                                without this it quietly falls back to software
+#   --enable-zero-copy           hand tiles to the compositor without a CPU copy
+# The rest are about a machine nobody sits in front of: no update checks, no crash
+# bubbles, no keyring prompt, no first-run wizard, no "restore pages?" after a power
+# cut. Anything policy-shaped rather than flag-shaped is in
+# /etc/chromium/policies/managed/.
+BROWSER_ARGS="--use-gl=egl --enable-gpu-rasterization --ignore-gpu-blocklist --enable-zero-copy"
+BROWSER_ARGS="$BROWSER_ARGS --noerrdialogs --disable-infobars --no-first-run"
+BROWSER_ARGS="$BROWSER_ARGS --no-default-browser-check --disable-session-crashed-bubble"
+BROWSER_ARGS="$BROWSER_ARGS --password-store=basic --check-for-update-interval=31536000"
 {% if pi_kiosk_mode == 'debug' %}
-# Debug session. Firefox is an ordinary window with its chrome (so devtools and the URL
-# bar are reachable) and is *not* relaunched when it exits - quitting it should leave a
-# usable desktop, not fight you for the screen. Openbox is the session leader instead:
-# when it exits (root menu -> Exit) the X session ends and .bash_profile starts a fresh
-# one. Right-click the desktop for a terminal.
-firefox "{{ pi_kiosk_url }}" &
+# Debug mode only. Binds to 127.0.0.1, so it is reachable over an ssh tunnel and from
+# nowhere else. Lets the page be driven and measured from a shell - `curl
+# localhost:9222/json` lists the tabs - instead of by poking XTEST key events at a
+# window and hoping they land.
+BROWSER_ARGS="$BROWSER_ARGS --remote-debugging-port=9222"
+{% endif %}
+{% else %}
+BROWSER=firefox
+BROWSER_ARGS=""
+{% endif %}
+
+{% if pi_kiosk_mode == 'debug' %}
+# Debug session. The browser is an ordinary window with its chrome (so devtools and the
+# URL bar are reachable) and is *not* relaunched when it exits - quitting it should
+# leave a usable desktop, not fight you for the screen. Openbox is the session leader
+# instead: when it exits (root menu -> Exit) the X session ends and .bash_profile
+# starts a fresh one. Right-click the desktop for a terminal.
+# shellcheck disable=SC2086  # BROWSER_ARGS is a word list on purpose
+$BROWSER $BROWSER_ARGS "{{ pi_kiosk_url }}" &
 
 exec openbox
 {% else %}
@@ -26,9 +57,10 @@ openbox &
 unclutter -idle 0.5 -root &
 
 # The loop is what takes the place of a WM's "keep something on screen" job: Openbox
-# manages the window, but nothing else would bring Firefox back if it died.
+# manages the window, but nothing else would bring the browser back if it died.
 while true; do
-  firefox --kiosk "{{ pi_kiosk_url }}"
+  # shellcheck disable=SC2086
+  $BROWSER --kiosk $BROWSER_ARGS "{{ pi_kiosk_url }}"
   sleep 2
 done
 {% endif %}