feat(channels): add optional command registrar capability interface

pkg/channels/interfaces.go

@@ -2,6 +2,8 @@ package channels
 
 import "context"
 
+import "github.com/sipeed/picoclaw/pkg/commands"
+
 // TypingCapable — channels that can show a typing/thinking indicator.
 // StartTyping begins the indicator and returns a stop function.
 // The stop function MUST be idempotent and safe to call multiple times.
@@ -39,3 +41,10 @@ type PlaceholderRecorder interface {
 	RecordTypingStop(channel, chatID string, stop func())
 	RecordReactionUndo(channel, chatID string, undo func())
 }
+
+// CommandRegistrarCapable is implemented by channels that can register
+// command menus with their upstream platform (e.g. Telegram BotCommand).
+// Channels that do not support platform-level command menus can ignore it.
+type CommandRegistrarCapable interface {
+	RegisterCommands(ctx context.Context, defs []commands.Definition) error
+}

pkg/channels/interfaces_command_test.go

@@ -0,0 +1,16 @@
+package channels
+
+import (
+	"context"
+	"testing"
+
+	"github.com/sipeed/picoclaw/pkg/commands"
+)
+
+type mockRegistrar struct{}
+
+func (mockRegistrar) RegisterCommands(context.Context, []commands.Definition) error { return nil }
+
+func TestCommandRegistrarCapable_Compiles(t *testing.T) {
+	var _ CommandRegistrarCapable = mockRegistrar{}
+}