fix(agent): group session unresponsive during team task execution (#266)

Two fixes:

1. Remove assistant prefill from team task reminders. The injected
   [user]+[assistant]+[user] pattern caused LLMs to treat the canned
   ack as "turn complete", returning NO_REPLY for every user message
   in group sessions with active tasks. Reminders are now merged into
   the user message as prefix tags.

2. Add PeerKind propagation to team notification routing. TaskTicker
   and progress notifications were missing PeerKind on InboundMessage,
   causing them to route to phantom DM sessions instead of the correct
   group session. PeerKind is now carried through event payloads,
   notify queue metadata, and all inbound message publications.

pkg/protocol/team_events.go

@@ -100,6 +100,7 @@ type TeamTaskEventPayload struct {
 	UserID           string `json:"user_id"`
 	Channel          string `json:"channel"`
 	ChatID           string `json:"chat_id"`
+	PeerKind         string `json:"peer_kind,omitempty"` // "group" or "direct" — for correct session routing (#266)
 	Timestamp        string `json:"timestamp"`
 
 	// Comment text preview (for team.task.commented events, truncated).