feat(tui): show background label on subagent line

Author: thdxr

packages/tui/src/routes/session/index.tsx

@@ -2262,7 +2262,7 @@ export function formatSubagentToolcalls(count: number) {
 }
 
 export function formatSubagentTitle(agent: string, description: string, background: boolean) {
-  return `${agent} Subagent${background ? " (background)" : ""} — ${description}`
+  return `${agent} Subagent — ${description}${background ? " [background]" : ""}`
 }
 
 export function formatSubagentRetry(attempt: number, message: string) {

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

@@ -175,7 +175,7 @@ describe("TUI inline tool wrapping", () => {
   test("keeps background state attached to the subagent identity", () => {
     expect(formatSubagentTitle("Explore", "Inspect renderer", false)).toBe("Explore Subagent — Inspect renderer")
     expect(formatSubagentTitle("Explore", "Inspect renderer", true)).toBe(
-      "Explore Subagent (background) — Inspect renderer",
+      "Explore Subagent — Inspect renderer [background]",
     )
   })