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/pi_hifiberry_amp/README.md

@@ -0,0 +1,6 @@
+# pi_hifiberry_amp
+
+Deactivates the Pi's onboard analog audio and activates a HiFiBerry
+amp/DAC overlay instead.
+
+**Key vars:** `hifiberry_overlay`

roles/pi_hifiberry_amp/handlers/main.yml

@@ -0,0 +1,3 @@
+---
+- name: Reboot
+  ansible.builtin.reboot:

roles/pi_hifiberry_amp/meta/main.yml

@@ -0,0 +1,3 @@
+---
+dependencies:
+  - role: pi_alsasetup

roles/pi_hifiberry_amp/tasks/main.yml

@@ -0,0 +1,13 @@
+---
+- name: Deactivate normal audio
+  ansible.builtin.lineinfile:
+    path: /boot/config.txt
+    regexp: "^#?dtparam=audio=on"
+    line: "#dtparam=audio=on"
+  notify: Reboot
+- name: Activate Hifiberry
+  ansible.builtin.lineinfile:
+    path: /boot/firmware/config.txt
+    regexp: "^#?dtoverlay=hifiberry-amp"
+    line: "dtoverlay={{ hifiberry_overlay }}"
+  notify: Reboot