Reject single bare word as implicit note shorthand

Single unrecognized words now print an error with usage hint instead of
being submitted as a note. Prevents typos from creating junk notes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

client/cmd/root.go

@@ -38,6 +38,9 @@ var rootCmd = &cobra.Command{
 		if len(args) == 0 {
 			return cmd.Help()
 		}
+		if len(args) == 1 {
+			return fmt.Errorf("unknown command %q\nTo add a note, use: kb \"%s ...\" or pass multiple words", args[0], args[0])
+		}
 		note := strings.Join(args, " ")
 		tags, _ := cmd.Flags().GetString("tags")
 		client := api.NewClient()
@@ -48,8 +51,8 @@ var rootCmd = &cobra.Command{
 func init() {
 	api.SetVersionInfo(Version, MinEngineVersion)
 	rootCmd.Version = Version
-	rootCmd.SetUsageTemplate(`Quick note taking:
-  kb "note text" [flags]
+	rootCmd.SetUsageTemplate(`Quick note taking (must be more than one word):
+  kb "note text here" [flags]
 
 Normal usage:
   kb [command] [flags]{{if .HasAvailableSubCommands}}

client/cmd/root_test.go

@@ -0,0 +1,54 @@
+package cmd
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestRootCmd_SingleWordRejected(t *testing.T) {
+	rootCmd.SetArgs([]string{"infow"})
+
+	var stderr bytes.Buffer
+	rootCmd.SetErr(&stderr)
+
+	err := rootCmd.Execute()
+	if err == nil {
+		t.Fatal("expected error for single bare word, got nil")
+	}
+
+	errMsg := err.Error()
+	if !strings.Contains(errMsg, `unknown command "infow"`) {
+		t.Errorf("expected error to mention unknown command, got: %s", errMsg)
+	}
+	if !strings.Contains(errMsg, "multiple words") {
+		t.Errorf("expected error to suggest multiple words, got: %s", errMsg)
+	}
+}
+
+func TestRootCmd_MultipleWordsNotRejected(t *testing.T) {
+	rootCmd.SetArgs([]string{"remember", "to", "update", "dns"})
+
+	err := rootCmd.Execute()
+	// Will fail at API call (no server), but should NOT be the "unknown command" error
+	if err != nil && strings.Contains(err.Error(), "unknown command") {
+		t.Errorf("multi-word input should not be rejected as unknown command, got: %s", err.Error())
+	}
+}
+
+func TestRootCmd_NoArgs_ShowsHelp(t *testing.T) {
+	rootCmd.SetArgs([]string{})
+
+	var stdout bytes.Buffer
+	rootCmd.SetOut(&stdout)
+
+	err := rootCmd.Execute()
+	if err != nil {
+		t.Fatalf("expected no error for zero args, got: %v", err)
+	}
+
+	output := stdout.String()
+	if !strings.Contains(output, "Available Commands") {
+		t.Errorf("expected help output, got: %s", output)
+	}
+}