Capture completion hints in command metadata

command.go

@@ -98,6 +98,8 @@ type FlagMeta struct {
 	Usage string
 	// Required reports whether execution requires the flag to be supplied.
 	Required bool
+	// Completion describes optional value suggestions.
+	Completion CompletionHint
 }
 
 // ArgumentMeta describes a positional command argument. Its name and usage are
@@ -107,6 +109,8 @@ type ArgumentMeta struct {
 	Name string
 	// Usage briefly describes the argument.
 	Usage string
+	// Completion describes optional value suggestions.
+	Completion CompletionHint
 }
 
 // Flag represents a typed binding for a command flag. Copies retain binding
@@ -202,13 +206,14 @@ func (c typedCommand[I]) bridgeFlags() []commandmeta.Flag {
 	for index, flag := range c.spec.Flags {
 		binding := flag.binding
 		flags[index] = commandmeta.Flag{
-			Name:     binding.meta.Name,
-			Short:    binding.meta.Short,
-			Usage:    binding.meta.Usage,
-			Default:  binding.defaultText,
-			Boolean:  binding.boolean,
-			Repeated: binding.repeated,
-			Required: binding.meta.Required,
+			Name:       binding.meta.Name,
+			Short:      binding.meta.Short,
+			Usage:      binding.meta.Usage,
+			Default:    binding.defaultText,
+			Boolean:    binding.boolean,
+			Repeated:   binding.repeated,
+			Required:   binding.meta.Required,
+			Completion: bridgeCompletion(binding.meta.Completion),
 		}
 	}
 	return flags
@@ -219,10 +224,11 @@ func (c typedCommand[I]) bridgeArguments() []commandmeta.Argument {
 	for index, argument := range c.spec.Arguments {
 		binding := argument.binding
 		arguments[index] = commandmeta.Argument{
-			Name:  binding.meta.Name,
-			Usage: binding.meta.Usage,
-			Min:   binding.min,
-			Max:   binding.max,
+			Name:       binding.meta.Name,
+			Usage:      binding.meta.Usage,
+			Min:        binding.min,
+			Max:        binding.max,
+			Completion: bridgeCompletion(binding.meta.Completion),
 		}
 	}
 	return arguments