Fix ansible-lint violations: FQCN, formatting, bugs, role renames

- Auto-fix FQCN, YAML formatting, jinja spacing, and free-form module
  syntax via ansible-lint --fix
- Fix comments misplaced inside module args by the auto-fixer
  (bluetooth-monitor, pi_standard_setup, pi_musicmouse)
- Fix notify: references left stale (lowercase) after handler names
  were re-cased, which would have silently broken reboot/restart
  handlers (pi_disable_onboard_bluetooth, pi_hifiberry_amp,
  pi_squeezelite, pi_standard_setup)
- Fix a task in pis/debmatic-install.yml missing its module name
  (apt_repository), which caused a real syntax-check failure
- Add missing play names, fix comment spacing, literal-compare idiom,
  and no-changed-when annotations
- Delete unused/broken roles/better-shell-env (unreferenced, invalid YAML)
- Rename all hyphenated role directories to underscore form to satisfy
  ansible-lint's role-name rule, updating every playbook/meta reference

Remaining lint findings (var-naming, package-latest, risky-file-permissions,
no-handler) intentionally left for follow-up per user decision.

roles/bluetooth_monitor/README.md

@@ -0,0 +1,12 @@
+# bluetooth_monitor
+
+Installs `my_btmonitor.py` (BLE scanning via `bleak`) as a systemd service
+that watches for nearby devices, publishes state over MQTT, and can restart
+the local BLE interface on a watchdog timeout.
+
+**Key vars:** `my_bt_monitor_watchdog_seconds`, `my_btmonitor_restart_ble_interface`,
+`my_btmonitor_mqtt_username`, `my_btmonitor_mqtt_password`
+
+`other/` is not part of the deployed role — it's a separate, standalone
+data-analysis project (Jupyter notebook, Dockerfile, collected CSV data) used
+to analyze data captured by the monitor.