* feat: register as Android default digital assistant
* fix: assistant role request fallback + always-attempt click
* remove: assistant role request row from Settings
The system-level assistant registration stays (VoiceInteractionService
+ ROLE_ASSISTANT, set via system Settings -> Default apps), but the
in-app Settings row is dropped: RequestRoleActivity fails to resolve
the caller on a plain startActivity ('Package name cannot be null or
empty'), so the button was a dead end. Removes the row, the
AssistantRole helper, and the now-unused strings.
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Co-authored-by: M57 <hy4ri@users.noreply.github.com>
