feat(commands): add command definitions and channel-aware registry

pkg/commands/definition.go

@@ -0,0 +1,9 @@
+package commands
+
+type Definition struct {
+	Name        string
+	Description string
+	Usage       string
+	Aliases     []string
+	Channels    []string
+}

pkg/commands/registry.go

@@ -0,0 +1,26 @@
+package commands
+
+type Registry struct {
+	defs []Definition
+}
+
+func NewRegistry(defs []Definition) *Registry {
+	return &Registry{defs: defs}
+}
+
+func (r *Registry) ForChannel(channel string) []Definition {
+	out := make([]Definition, 0, len(r.defs))
+	for _, d := range r.defs {
+		if len(d.Channels) == 0 {
+			out = append(out, d)
+			continue
+		}
+		for _, ch := range d.Channels {
+			if ch == channel {
+				out = append(out, d)
+				break
+			}
+		}
+	}
+	return out
+}

pkg/commands/registry_test.go

@@ -0,0 +1,21 @@
+package commands
+
+import "testing"
+
+func TestRegistry_FilterByChannel(t *testing.T) {
+	defs := []Definition{
+		{Name: "help", Description: "Show help"},
+		{Name: "admin", Description: "Admin only", Channels: []string{"telegram"}},
+	}
+	r := NewRegistry(defs)
+
+	gotTG := r.ForChannel("telegram")
+	if len(gotTG) != 2 {
+		t.Fatalf("telegram defs = %d, want 2", len(gotTG))
+	}
+
+	gotWA := r.ForChannel("whatsapp")
+	if len(gotWA) != 1 || gotWA[0].Name != "help" {
+		t.Fatalf("whatsapp defs = %+v, want only help", gotWA)
+	}
+}