fix(tui): keep background marker with subagent label (#30271)

packages/opencode/test/cli/tui/inline-tool-wrap-snapshot.test.tsx

@@ -3,6 +3,7 @@ import { For } from "solid-js"
 import { testRender, type JSX } from "@opentui/solid"
 import {
   formatCompletedSubagentDetail,
+  formatSubagentTitle,
   formatSubagentToolcalls,
   InlineToolRow,
 } from "../../../src/cli/cmd/tui/routes/session/index"
@@ -147,6 +148,13 @@ describe("TUI inline tool wrapping", () => {
     expect(formatSubagentToolcalls(0)).toBe("0 toolcalls")
   })
 
+  test("keeps background state attached to the subagent identity", () => {
+    expect(formatSubagentTitle("Explore", "Inspect renderer", false)).toBe("Explore Task — Inspect renderer")
+    expect(formatSubagentTitle("Explore", "Inspect renderer", true)).toBe(
+      "Explore Task (background) — Inspect renderer",
+    )
+  })
+
   test("snapshots consecutive grep, glob, and read rows at a narrow width", async () => {
     expect(await renderFrame(() => <Fixture />, { width: 72, height: 12 })).toMatchSnapshot()
   })