fix(test): update dynamic-agent-prompt-builder test to expect task_id

Same session_id->task_id migration as the atlas hook test.

src/agents/dynamic-agent-prompt-builder.test.ts

@@ -244,7 +244,7 @@ describe("buildNonClaudePlannerSection", () => {
 
     //#then
     expect(result).toContain("Plan Agent")
-    expect(result).toContain("session_id")
+    expect(result).toContain("task_id")
     expect(result).toContain("Multi-step")
   })