feat (tui): agents dialog (#1802)

packages/tui/internal/app/app.go

@@ -70,6 +70,9 @@ type ModelSelectedMsg struct {
 	Provider opencode.Provider
 	Model    opencode.Model
 }
+type AgentSelectedMsg struct {
+	Agent opencode.Agent
+}
 type SessionClearedMsg struct{}
 type CompactSessionMsg struct{}
 type SendPrompt = Prompt