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/tasks/main.yml

@@ -5,14 +5,23 @@
       - xserver-xorg
       - xinit
       - x11-xserver-utils
-      # Without a window manager, Firefox's request to go full-screen (which is all
+      # Without a window manager, a browser's request to go full-screen (which is all
       # --kiosk does) has nobody to answer it, and it settles for its default window
       # size in the corner of the screen. Openbox answers it, and nothing else.
       - openbox
-      - firefox-esr
       - unclutter
     cache_valid_time: 7200
 
+- name: Browser
+  # Chromium comes from archive.raspberrypi.com, not Debian: that build carries the
+  # "+rpt" suffix and Raspberry Pi's own patches for the V3D GPU on this board. Debian
+  # also ships a much older `chromium`, so pinning the wrong archive here would quietly
+  # undo the reason for choosing it.
+  ansible.builtin.apt:
+    name: "{{ 'chromium' if pi_kiosk_browser == 'chromium' else 'firefox-esr' }}"
+    cache_valid_time: 7200
+  notify: Reload systemd and restart getty
+
 - name: Debugging tools for the attached screen
   # Only pulled in for pi_kiosk_mode=debug; apt does not take them away again when the
   # host goes back to kiosk mode, which is fine - they are inert and small.
@@ -21,6 +30,9 @@
       - xterm       # a terminal that is ours, whatever x-terminal-emulator points at
       - x11-utils   # xwininfo, xprop: is the window actually the size of the screen?
       - mesa-utils  # glxinfo, glxgears: is anything accelerated, or is this llvmpipe?
+      - xdotool     # drive the UI from ssh, so a measurement can be taken on a real
+                    # screen rather than an idle one
+      - scrot       # and see what that screen actually shows, over ssh
     cache_valid_time: 7200
   when: pi_kiosk_mode == 'debug'
 
@@ -81,7 +93,7 @@
     mode: "0644"
   notify: Reload systemd and restart getty
 
-- name: Install .xinitrc (starts Openbox, then Firefox)
+- name: Install .xinitrc (starts Openbox, then the browser)
   ansible.builtin.template:
     src: xinitrc.j2
     dest: "/home/{{ pi_kiosk_user }}/.xinitrc"
@@ -90,18 +102,24 @@
     mode: "0755"
   notify: Reload systemd and restart getty
 
-- name: Ensure firefox-esr policy directory exists
+- name: Ensure the browser policy directory exists
   ansible.builtin.file:
-    path: /etc/firefox-esr
+    path: "{{ '/etc/chromium/policies/managed' if pi_kiosk_browser == 'chromium' else '/etc/firefox-esr' }}"
     state: directory
     mode: "0755"
-  # apt normally creates this; a backstop in case the package layout doesn't
+  # The packages normally create these; a backstop in case a layout changes
 
-- name: Install Firefox enterprise policy (suppress session-restore/update prompts)
+- name: Install the browser's enterprise policy
+  # Everything that is a setting rather than a startup flag: no sign-in, no sync, no
+  # metrics, no password manager, no translate bar. The flags themselves are in
+  # .xinitrc, where they have to be.
   ansible.builtin.copy:
-    src: policies.json
-    dest: /etc/firefox-esr/policies.json
+    src: "{{ 'chromium-policies.json' if pi_kiosk_browser == 'chromium' else 'policies.json' }}"
+    dest: >-
+      {{ '/etc/chromium/policies/managed/kiosk.json'
+         if pi_kiosk_browser == 'chromium' else '/etc/firefox-esr/policies.json' }}
     mode: "0644"
+  notify: Reload systemd and restart getty
 
 - name: Ensure the Openbox config directories exist
   # Both levels explicitly, and owned by the user: a file: task creates missing parents