9p: add /agents file listing available agent configs

main.go

@@ -315,6 +315,22 @@ func NewRootStore() *fs.Tree {
 		"help": func() ([]byte, error) {
 			return os.ReadFile(helpPath)
 		},
+		"agents": func() ([]byte, error) {
+			var sb strings.Builder
+			for _, dir := range agent.AgentsDirs() {
+				entries, err := os.ReadDir(dir)
+				if err != nil {
+					continue
+				}
+				for _, e := range entries {
+					if !e.IsDir() && strings.HasSuffix(e.Name(), ".json") {
+						sb.WriteString(strings.TrimSuffix(e.Name(), ".json"))
+						sb.WriteByte('\n')
+					}
+				}
+			}
+			return []byte(sb.String()), nil
+		},
 	}
 	notBlocking := func(context.Context, string) ([]byte, string, error) {
 		return nil, "", fmt.Errorf("blocking read not supported")

server/server.go

@@ -1013,7 +1013,7 @@ func (s *Server) buildDirData(path string) []byte {
 	var dirs []plan9.Dir
 
 	if path == "/" {
-		rootEntries := []string{"backends", "ctl", "help", "models", "s"}
+		rootEntries := []string{"agents", "backends", "ctl", "help", "models", "s"}
 		for _, name := range rootEntries {
 			fpath := "/" + name
 			st := s.makeStat(fpath)