When sending a message to a phone number like +12622102921, the
resolveChatGuidForTarget function was finding and returning a GROUP
CHAT containing that phone number instead of a direct DM chat.
The bug was in the participantMatch fallback logic which matched ANY
chat containing the phone number as a participant, including groups.
This fix adds a check to ensure participantMatch only considers DM
chats (identified by ';-;' separator in the chat GUID). Group chats
(identified by ';+;' separator) are now explicitly excluded from
handle-based matching.
If a phone number only exists in a group chat (no direct DM exists),
the function now correctly returns null, which causes the send to
fail with a clear error rather than accidentally messaging a group.
Added test case to verify this behavior.
f997a3f395