_handle_location_message and _handle_media_message were skipped when the
observe-unmentioned-group-messages feature landed (a9db0e2c7). Both handlers
now:
1. Check _should_observe_unmentioned_group_message on the skipped path and
call _observe_unmentioned_group_message so group chatter is stored as
shared session context even when the bot is not addressed.
2. Call _apply_telegram_group_observe_attribution on the triggered path so
the dispatched event uses the shared (user_id=None) group session instead
of the per-user session, letting the model see previously observed context.
For stickers the attribution is applied after _handle_sticker completes
(which overwrites event.text with the vision description); for all other
media types it is applied once after caption cleaning.
Four new tests cover the observe and attribution paths for both handlers.
6c26727bb3