fix(web): deduplicate subagent navigation

packages/host/apiproxy/src/api/events.ts

@@ -90,9 +90,9 @@ export type MuxFrame =
   | { type: 'stream/error'; error: RpcError }
 
 /**
- * Host stream frames. session-added carries the lineage anchor, the project
- * cwd, and the blank bit (the list-summary fields a client cannot wait for a
- * refresh to learn); the frame fires at session/created, so blank is
+ * Host stream frames. session-added carries the lineage anchor, product
+ * origin, project cwd, and blank bit (the list-summary fields a client cannot
+ * wait for a refresh to learn); the frame fires at session/created, so blank is
  * constantly true — clients flip it on the session's first
  * `host/session-status(running:true)` (a blank session never runs), and a
  * reconnecting client takes `session.list`'s summary.blank as authoritative.
@@ -106,7 +106,14 @@ export type MuxFrame =
  * workspace-changed — `workspace.list` re-baselines it on reconnect).
  */
 export type HostFrame =
-  | { type: 'host/session-added'; sessionId: SessionId; blank: boolean; parentSessionId?: SessionId; cwd?: string }
+  | {
+    type: 'host/session-added'
+    sessionId: SessionId
+    blank: boolean
+    parentSessionId?: SessionId
+    origin?: 'subagent'
+    cwd?: string
+  }
   | { type: 'host/session-removed'; sessionId: SessionId }
   | { type: 'host/session-status'; sessionId: SessionId; running: boolean }
   | { type: 'host/agent-error'; sessionId: SessionId; message: string }