Add oo CLI support for mail attachment downloads.

This exposes the canonical attachment download path via oo mails so downstream tools like 2dph can migrate off local OnlyOffice mail adapters without taking a direct module dependency first.

cmd/oo/mails.go

@@ -22,6 +22,7 @@ func init() {
 	mailsCmd.AddCommand(mailsFoldersCmd())
 	mailsCmd.AddCommand(mailsListCmd())
 	mailsCmd.AddCommand(mailsGetCmd())
+	mailsCmd.AddCommand(mailsDownloadAttachmentCmd())
 	mailsCmd.AddCommand(mailsDraftCmd())
 	mailsCmd.AddCommand(mailsAttachCmd())
 	mailsCmd.AddCommand(mailsDraftInvoiceCmd())
@@ -131,6 +132,48 @@ func mailsGetCmd() *cobra.Command {
 	}
 }
 
+func mailsDownloadAttachmentCmd() *cobra.Command {
+	var outPath string
+	cmd := &cobra.Command{
+		Use:   "download-attachment ATTACHMENT_ID",
+		Short: "Download a mail attachment by attachment id",
+		Long: `Download a raw attachment from OnlyOffice Mail's download.ashx handler.
+
+Example:
+  oo mails download-attachment 12345 --out /tmp/attach.bin
+`,
+		Args: cobra.ExactArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if strings.TrimSpace(outPath) == "" {
+				return fmt.Errorf("--out is required")
+			}
+			c, err := newOO(cmd)
+			if err != nil {
+				return err
+			}
+			body, err := c.DownloadMailAttachment(cmd.Context(), args[0])
+			if err != nil {
+				return err
+			}
+			if err := writeMailAttachment(outPath, body); err != nil {
+				return err
+			}
+			if outputFormat == "json" {
+				printObject(map[string]any{
+					"attachmentId": args[0],
+					"bytes":        len(body),
+					"path":         outPath,
+				})
+				return nil
+			}
+			fmt.Printf("saved %d bytes to %s\n", len(body), outPath)
+			return nil
+		},
+	}
+	cmd.Flags().StringVar(&outPath, "out", "", "output file path")
+	return cmd
+}
+
 func mailsDraftCmd() *cobra.Command {
 	var from, to, cc, bcc, subject, body, html string
 	var id int64
@@ -297,6 +340,13 @@ func formatInvoiceCostEUR(v any) string {
 	return s
 }
 
+func writeMailAttachment(path string, body []byte) error {
+	if strings.TrimSpace(path) == "" {
+		return fmt.Errorf("attachment output path is required")
+	}
+	return os.WriteFile(path, body, 0o644)
+}
+
 func mailsDeleteCmd() *cobra.Command {
 	return &cobra.Command{
 		Use:     "delete ID [ID...]",

cmd/oo/mails_cli_test.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestWriteMailAttachment(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "attach.bin")
+	body := []byte("payload")
+	if err := writeMailAttachment(path, body); err != nil {
+		t.Fatalf("writeMailAttachment: %v", err)
+	}
+	got, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("ReadFile: %v", err)
+	}
+	if string(got) != string(body) {
+		t.Fatalf("body = %q", got)
+	}
+}
+
+func TestWriteMailAttachmentRequiresPath(t *testing.T) {
+	if err := writeMailAttachment("", []byte("x")); err == nil {
+		t.Fatal("expected error for empty path")
+	}
+}

cmd/oo/main.go

@@ -13,7 +13,7 @@
 //	oo cases         list | create | delete | member-add
 //	oo crm-tasks     list | create | delete | categories
 //	oo crm           cleanup
-//	oo mails         accounts | folders | list | get | draft | attach | draft-invoice | delete
+//	oo mails         accounts | folders | list | get | download-attachment | draft | attach | draft-invoice | delete
 //	oo invoices      list | get | create | update | pdf | pdf-cleanup | status | delete | items …
 //
 // CRM association rules: docs/crm-associations.md