Channels previously deleted downloaded media files via defer os.Remove,
racing with the async Agent consumer. Introduce MediaStore to decouple
file ownership: channels register files on download, Agent releases them
after processing via ReleaseAll(scope).
- New pkg/media with MediaStore interface + FileMediaStore implementation
- InboundMessage gains MediaScope field for lifecycle tracking
- BaseChannel gains SetMediaStore/GetMediaStore + BuildMediaScope helper
- Manager injects MediaStore into channels; AgentLoop releases on completion
- Telegram, Discord, Slack, OneBot, LINE channels migrated from defer
os.Remove to store.Store() with media:// refs
Add bus.Peer struct and explicit Peer/MessageID fields to InboundMessage,
replacing the implicit peer_kind/peer_id/message_id metadata convention.
- Add Peer{Kind, ID} type to pkg/bus/types.go
- Extend InboundMessage with Peer and MessageID fields
- Change BaseChannel.HandleMessage signature to accept peer and messageID
- Adapt all 12 channel implementations to pass structured peer/messageID
- Simplify agent extractPeer() to read msg.Peer directly
- extractParentPeer unchanged (parent_peer still via metadata)
Hoshina