Filament's sanitizer strips data-id, data-label and data-char from
mention spans, breaking both display (unstyled @mention) and editing
(@-only shown in RichEditor). Register a package-scoped sanitizer that
explicitly allows these attributes on span elements.
Also fix double-replacement bug in renderBodyWithMentions() where both
the rich-editor regex and str_replace fallback could run on the same
mention, producing nested styled spans.
541d11ab90