feat(tui): allow backgrounding synchronous subagents (#30488)

packages/opencode/test/cli/run/footer.view.test.tsx

@@ -185,6 +185,7 @@ async function renderFooter(
           subagent={subagents}
           theme={RUN_THEME_FALLBACK}
           tuiConfig={config}
+          backgroundSubagents={true}
           agent="opencode"
           onSubmit={input.onSubmit ?? (() => true)}
           onPermissionReply={() => {}}
@@ -613,6 +614,7 @@ test("direct footer shows editable prompts and additional queued work while runn
           ]}
           theme={RUN_THEME_FALLBACK}
           tuiConfig={tuiConfig}
+          backgroundSubagents={true}
           agent="opencode"
           onSubmit={() => true}
           onPermissionReply={() => {}}
@@ -647,7 +649,7 @@ test("direct footer shows editable prompts and additional queued work while runn
 
   try {
     await app.renderOnce()
-    expect(app.captureCharFrame()).toContain("interrupt • 1 agent ctrl+x down • 1 queued ctrl+x q")
+    expect(app.captureCharFrame()).toContain("interrupt • 1 agent ctrl+x down • ctrl+b background • 1 queued ctrl+x q")
     expect(app.captureCharFrame()).toContain("2 queued")
     expect(app.captureCharFrame()).not.toContain("to view")
     expect(app.captureCharFrame()).not.toContain("edit/remove")