pub fn parse_mentions(content: &str) -> Vec<String>Expand description
Extract @mentions from message content.
Matches @username patterns where usernames can contain alphanumerics, hyphens,
and underscores. Stops at whitespace, punctuation (except - and _), or end of
string. Skips email-like patterns (user@domain) by requiring the @ to be at
the start of the string or preceded by whitespace.
Returns a deduplicated list of mentioned usernames (without the @ prefix),
preserving first-occurrence order.