pub fn parse_message_id(id: &str) -> Result<(String, u64), String>Expand description
Parse a human-readable message ID back into (room_id, seq).
Expects the format "<room>:<seq>" produced by format_message_id.
Splits on the last colon so room IDs that themselves contain colons are
handled correctly (e.g. "namespace:room:42" → ("namespace:room", 42)).
Returns Err(String) if the input has no colon or if the part after the
last colon cannot be parsed as a u64.