fix(graph): filter system messages from particles + fix direction

- Skip idle_notification, shutdown, and other JSON system messages
  (was showing {"type":"idle_notificatio... as particle labels)
- Skip system_notification source messages
- Skip messages with < 3 chars

src/renderer/features/agent-graph/adapters/TeamGraphAdapter.ts

@@ -494,6 +494,9 @@ export class TeamGraphAdapter {
       if (this.#seenMessageIds.has(msgKey)) continue;
       this.#seenMessageIds.add(msgKey);
 
+      // Skip system/noise messages (idle notifications, JSON blobs)
+      if (TeamGraphAdapter.#isSystemMessage(msg)) continue;
+
       const edgeId = TeamGraphAdapter.#resolveMessageEdge(msg, teamName, leadId, leadName, edges);
       if (!edgeId) continue;
 
@@ -691,6 +694,18 @@ export class TeamGraphAdapter {
     return `member:${teamName}:${name}`;
   }
 
+  /** Filter out system/noise messages that shouldn't show as particles */
+  static #isSystemMessage(msg: InboxMessage): boolean {
+    const text = msg.text ?? '';
+    // JSON system messages (idle_notification, shutdown, etc.)
+    if (text.startsWith('{"type":') || text.startsWith('{"type" :')) return true;
+    // Very short system messages
+    if (text.length < 3) return true;
+    // System notification source
+    if (msg.source === 'system_notification') return true;
+    return false;
+  }
+
   static #buildParticleLabel(
     text: string | undefined,
     kind: 'inbox' | 'comment',