feat: [US-049] - Node editing lock indicators

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/lib/collaboration/realtime.ts

@@ -20,6 +20,13 @@ export type RemoteCursor = {
   lastUpdated: number
 }
 
+export type NodeLock = {
+  nodeId: string
+  userId: string
+  displayName: string
+  lockedAt: number
+}
+
 type RealtimeCallbacks = {
   onConnectionStateChange: (state: ConnectionState) => void
   onPresenceSync?: (users: PresenceUser[]) => void
@@ -27,6 +34,7 @@ type RealtimeCallbacks = {
   onPresenceLeave?: (user: PresenceUser) => void
   onChannelSubscribed?: (channel: RealtimeChannel) => void
   onCursorUpdate?: (cursor: RemoteCursor) => void
+  onNodeLockUpdate?: (lock: NodeLock | null, userId: string) => void
 }
 
 const HEARTBEAT_INTERVAL_MS = 30_000
@@ -109,6 +117,20 @@ export class RealtimeConnection {
           lastUpdated: Date.now(),
         })
       })
+      .on('broadcast', { event: 'node-lock' }, ({ payload }) => {
+        if (payload.userId === this.userId) return
+        if (payload.nodeId) {
+          this.callbacks.onNodeLockUpdate?.({
+            nodeId: payload.nodeId,
+            userId: payload.userId,
+            displayName: payload.displayName,
+            lockedAt: payload.lockedAt,
+          }, payload.userId)
+        } else {
+          // null nodeId means unlock
+          this.callbacks.onNodeLockUpdate?.(null, payload.userId)
+        }
+      })
       .subscribe(async (status) => {
         if (this.isDestroyed) return
 
@@ -167,6 +189,20 @@ export class RealtimeConnection {
     })
   }
 
+  broadcastNodeLock(nodeId: string | null): void {
+    if (!this.channel) return
+    this.channel.send({
+      type: 'broadcast',
+      event: 'node-lock',
+      payload: {
+        userId: this.userId,
+        displayName: this.displayName,
+        nodeId,
+        lockedAt: Date.now(),
+      },
+    })
+  }
+
   private async createSession(): Promise<void> {
     try {
       await this.supabase.from('collaboration_sessions').upsert(