feat: message reactions + link/image previews

Reactions (full stack):
- Wire: MsgReaction peer message (reaction_mid, reaction_emoji)
- Store: reactions table (mid, emoji, from_peer), SaveReaction, ReactionsForRoom
- Daemon: CmdSendReaction IPC command; EvtReaction IPC event; stored reactions
  replayed to newly-connected IPC clients alongside history
- Web UI: reactions state (mid → emoji → [fromId]); hover a message to reveal
  a + button; click opens a 6-emoji picker (👍❤️😂😮😢🙏); reaction chips
  appear below the message with count and tooltip; own reactions highlighted

Link/image previews:
- URLs in message text rendered as clickable <a> links
- Image URLs (.jpg/.jpeg/.png/.gif/.webp/blob:/data:image) rendered as inline
  thumbnails (max 320×200px) below the link

Also scoped push notifications architecture in FUTURE.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/ipc/ipc.go

@@ -244,6 +244,34 @@ func handleClient(conn net.Conn, mgr *netmgr.Manager) {
 				})
 			}
 
+		case proto.CmdSendReaction:
+			n := mgr.Resolve(cmd.NetworkID)
+			if n == nil {
+				send(errMsg("send_reaction: not joined to any network"))
+				continue
+			}
+			if cmd.ReactionMID == "" || cmd.ReactionEmoji == "" {
+				send(errMsg("send_reaction: reaction_mid and reaction_emoji are required"))
+				continue
+			}
+			wire, err := json.Marshal(proto.PeerMessage{
+				Type:          proto.MsgReaction,
+				ReactionMID:   cmd.ReactionMID,
+				ReactionEmoji: cmd.ReactionEmoji,
+			})
+			if err != nil {
+				continue
+			}
+			n.Mesh.Broadcast(wire)
+			n.Mesh.SaveReaction(cmd.ReactionMID, cmd.ReactionEmoji, string(n.Identity.PeerID()))
+			n.Mesh.Emit(proto.IpcMessage{
+				Type:          proto.EvtReaction,
+				NetworkID:     n.ID,
+				PeerID:        ptr(n.Identity.PeerID()),
+				ReactionMID:   cmd.ReactionMID,
+				ReactionEmoji: cmd.ReactionEmoji,
+			})
+
 		case proto.CmdCreateRoom:
 			n := mgr.Resolve(cmd.NetworkID)
 			if n == nil {
@@ -505,6 +533,25 @@ func sendStoredHistory(mgr *netmgr.Manager, send func(proto.IpcMessage)) {
 			Room:      room,
 			Messages:  msgs,
 		})
+		// Send stored reactions for this room's messages.
+		rxns, err := n.Store.ReactionsForRoom(room)
+		if err != nil {
+			continue
+		}
+		for mid, byEmoji := range rxns {
+			for emoji, fromPeers := range byEmoji {
+				for _, fromPeer := range fromPeers {
+					pid := proto.PeerID(fromPeer)
+					send(proto.IpcMessage{
+						Type:          proto.EvtReaction,
+						NetworkID:     n.ID,
+						PeerID:        &pid,
+						ReactionMID:   mid,
+						ReactionEmoji: emoji,
+					})
+				}
+			}
+		}
 	}
 }
 

internal/mesh/mesh.go

@@ -146,6 +146,17 @@ func (m *Mesh) AddPeer(conn *PeerConn) {
 	})
 }
 
+// SaveReaction persists a reaction if a store is configured.
+// Duplicate (mid, emoji, fromPeer) triples are silently dropped.
+func (m *Mesh) SaveReaction(mid, emoji, fromPeer string) {
+	if m.Store == nil {
+		return
+	}
+	if err := m.Store.SaveReaction(mid, emoji, fromPeer); err != nil {
+		log.Printf("mesh: store reaction %s/%s: %v", mid, emoji, err)
+	}
+}
+
 // SaveMessage persists a chat message if a store is configured.
 // Duplicate mids are silently dropped.
 func (m *Mesh) SaveMessage(msg *proto.ChatMessage) {

internal/mesh/peer.go

@@ -307,6 +307,18 @@ func dispatchPeerMessage(msg proto.PeerMessage, from proto.PeerID, m *Mesh) {
 	case proto.MsgHistoryChunk:
 		go m.HandleHistoryChunk(msg.Room, msg.History)
 
+	case proto.MsgReaction:
+		if msg.ReactionMID == "" || msg.ReactionEmoji == "" {
+			return
+		}
+		m.SaveReaction(msg.ReactionMID, msg.ReactionEmoji, string(from))
+		m.emit(proto.IpcMessage{
+			Type:          proto.EvtReaction,
+			PeerID:        peerIDPtr(from),
+			ReactionMID:   msg.ReactionMID,
+			ReactionEmoji: msg.ReactionEmoji,
+		})
+
 	case proto.MsgPing:
 		log.Printf("mesh: ping from %s", from.Short())
 	case proto.MsgPong:

internal/proto/proto.go

@@ -51,6 +51,7 @@ const (
 	MsgPong            MsgType = "pong"
 	MsgHistoryRequest  MsgType = "history_request"
 	MsgHistoryChunk    MsgType = "history_chunk"
+	MsgReaction        MsgType = "reaction"
 )
 
 // PmMessage is a private message sent directly over a single peer link (§8 "pm").
@@ -97,6 +98,10 @@ type PeerMessage struct {
 	// history_chunk fields
 	History     []HistoryEntry `json:"history,omitempty"`
 	HistoryDone bool           `json:"history_done,omitempty"`
+
+	// reaction fields
+	ReactionMID   string `json:"reaction_mid,omitempty"`
+	ReactionEmoji string `json:"reaction_emoji,omitempty"`
 }
 
 // ResumableFile describes a partially-downloaded file found on daemon startup.
@@ -280,6 +285,7 @@ const (
 	CmdListShares     IpcMsgType = "list_shares"       // returns shares_list event
 	CmdCreateRoom       IpcMsgType = "create_room"        // field: room (name)
 	CmdSetDownloadDir   IpcMsgType = "set_download_dir"   // set per-network download directory at runtime; fields: network_id, path
+	CmdSendReaction     IpcMsgType = "send_reaction"      // fields: network_id, reaction_mid, reaction_emoji
 
 	// Events (daemon → UI)
 	EvtMessageReceived  IpcMsgType = "message_received"
@@ -302,6 +308,7 @@ const (
 	EvtRoomCreated      IpcMsgType = "room_created"    // field: room (name)
 	EvtHistoryLoaded      IpcMsgType = "history_loaded"       // fields: room, messages
 	EvtResumableTransfers IpcMsgType = "resumable_transfers"  // field: resumable_files
+	EvtReaction           IpcMsgType = "reaction"             // fields: reaction_mid, reaction_emoji, peer_id
 )
 
 // NetworkInfo summarises one joined network for state_snapshot and network_joined events.
@@ -359,6 +366,8 @@ type IpcMessage struct {
 	Files          []FileEntry    `json:"files,omitempty"`
 	Messages        []ChatMessage   `json:"messages,omitempty"`          // history_loaded
 	ResumableFiles  []ResumableFile `json:"resumable_files,omitempty"`   // resumable_transfers
+	ReactionMID     string          `json:"reaction_mid,omitempty"`      // reaction
+	ReactionEmoji   string          `json:"reaction_emoji,omitempty"`    // reaction
 	Shares         []ShareEntry `json:"shares,omitempty"`
 	ShareNetworks  []string     `json:"network_ids,omitempty"` // for add_share command: scope to specific network IDs, or ["*"] for global
 	// export_identity / import_identity

internal/store/store.go

@@ -38,10 +38,19 @@ CREATE TABLE IF NOT EXISTS rooms (
 
 // migrations run after the base schema. ALTER TABLE ADD COLUMN fails with
 // "duplicate column name" on subsequent opens — we swallow that error.
+// CREATE TABLE IF NOT EXISTS and CREATE INDEX IF NOT EXISTS are idempotent.
 var migrations = []string{
 	// EXT-007: canonical message ID for history dedup (NULL for pre-feature messages).
 	`ALTER TABLE messages ADD COLUMN msg_id TEXT`,
 	`CREATE UNIQUE INDEX IF NOT EXISTS idx_messages_msg_id ON messages (msg_id) WHERE msg_id IS NOT NULL`,
+	// Reactions: (mid, emoji, from_peer) triple is the unique dedup key.
+	`CREATE TABLE IF NOT EXISTS reactions (
+		mid        TEXT NOT NULL,
+		emoji      TEXT NOT NULL,
+		from_peer  TEXT NOT NULL,
+		reacted_at DATETIME NOT NULL,
+		PRIMARY KEY (mid, emoji, from_peer)
+	)`,
 }
 
 // Store is a local SQLite-backed message and peer store.
@@ -208,6 +217,43 @@ func (s *Store) KnownPeers() (map[proto.PeerID]string, error) {
 	return out, rows.Err()
 }
 
+// SaveReaction persists a reaction. Duplicate (mid, emoji, from_peer) triples are silently ignored.
+func (s *Store) SaveReaction(mid, emoji, fromPeer string) error {
+	_, err := s.db.Exec(
+		`INSERT OR IGNORE INTO reactions (mid, emoji, from_peer, reacted_at) VALUES (?, ?, ?, ?)`,
+		mid, emoji, fromPeer, time.Now().UTC(),
+	)
+	return err
+}
+
+// ReactionsForRoom returns all reactions for messages in a given room.
+// Result: mid → emoji → []fromPeer (ordered by reaction time).
+func (s *Store) ReactionsForRoom(room string) (map[string]map[string][]string, error) {
+	rows, err := s.db.Query(`
+		SELECT r.mid, r.emoji, r.from_peer
+		FROM reactions r
+		JOIN messages m ON m.mid = r.mid
+		WHERE m.room = ?
+		ORDER BY r.reacted_at
+	`, room)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := make(map[string]map[string][]string)
+	for rows.Next() {
+		var mid, emoji, from string
+		if err := rows.Scan(&mid, &emoji, &from); err != nil {
+			return nil, err
+		}
+		if out[mid] == nil {
+			out[mid] = make(map[string][]string)
+		}
+		out[mid][emoji] = append(out[mid][emoji], from)
+	}
+	return out, rows.Err()
+}
+
 func nullableString(s string) any {
 	if s == "" {
 		return nil