fix(web): deduplicate subagent navigation

packages/core/agent/src/index.ts

@@ -48,9 +48,9 @@ export interface CreateAgentOptions {
   readonly sessionId: SessionId
   /**
    * Session creation metadata: validated absolute `cwd`, `parentSession`
-   * fork lineage, the `seedLength` seed boundary, and the `delegationDepth`
-   * recursion budget. Mirrors the
-   * `cwd`/`parentSession`/`seedLength`/`delegationDepth` fields of
+   * fork lineage, the `seedLength` seed boundary, the coarse `origin`
+   * classification, and the `delegationDepth` recursion budget. Mirrors the
+   * `cwd`/`parentSession`/`seedLength`/`origin`/`delegationDepth` fields of
    * {@link CreateSessionOptions.meta} in dsh-session (the internal-only
    * `createdAt`, used when reconstructing a persisted session, is deliberately
    * excluded — a factory caller never sets it). This is durable session data,
@@ -61,6 +61,7 @@ export interface CreateAgentOptions {
     readonly cwd?: string
     readonly parentSession?: SessionId
     readonly seedLength?: number
+    readonly origin?: 'subagent'
     readonly delegationDepth?: number
   }
   /**