refactor: remove sync command, merge into pull, add diff hints

openboot sync is removed — openboot pull now owns all the apply logic.
The interactive multi-select was removed with sync; pull auto-applies
all remote changes (use --dry-run to preview first).

diff now shows 'openboot pull / openboot push' hints when changes exist
so the direction is always obvious.

Author: fullstackjam

internal/cli/diff.go

@@ -8,6 +8,7 @@ import (
 	"github.com/openbootdotdev/openboot/internal/config"
 	"github.com/openbootdotdev/openboot/internal/diff"
 	"github.com/openbootdotdev/openboot/internal/snapshot"
+	"github.com/openbootdotdev/openboot/internal/ui"
 	"github.com/spf13/cobra"
 )
 
@@ -84,6 +85,12 @@ func runDiff(cmd *cobra.Command) error {
 	}
 
 	diff.FormatTerminal(result, packagesOnly)
+
+	if result.HasChanges() {
+		fmt.Println()
+		ui.Muted("  Apply remote → local: openboot pull   •   Upload local → remote: openboot push")
+	}
+
 	return nil
 }