bare_address sliced trimmed[..7] after a len() >= 7 check — byte
count against a byte slice is fine, but the guard and the slice
disagree once the text is lossy-decoded elsewhere; an ATTENDEE line
whose value opens with a multibyte run panicked the reminder source
on a feed the operator does not control. The slice is get(..7) now,
and a test feeds multibyte prefixes through both the ATTENDEE and
ORGANIZER paths.