#3343: recognize PageMaker .pmd on open with a clear message

## Summary
Opening or placing a .pmd file now fails with a dedicated unsupported-format
hint (like DWG and PICT), telling users to export PDF or EPS from PageMaker
instead of a generic unknown-format error. document.formats lists PageMaker
in its unsupported table.

## Tests
- formats_list_dxf_and_what_can_not_be_written
- dwg_and_pict_say_what_to_use_instead (includes brochure.PMD open)

Part of storytold/vectorcraft#3343

Co-authored-by: nrq6993-a11y <nrq6993-a11y@users.noreply.github.com>

crates/engine/src/cmd/fileio/dxf.rs

@@ -94,6 +94,12 @@ pub const UNSUPPORTED: &[Unsupported] = &[
         extensions: &["pict", "pct", "pic"],
         hint: "PICT is a retired format and is not supported: convert the file to PDF or PNG first",
     },
+    Unsupported {
+        id: "pmd",
+        label: "PageMaker",
+        extensions: &["pmd"],
+        hint: "PageMaker (.pmd) is not supported: open the layout in PageMaker and export PDF or EPS, or place a PDF export here",
+    },
 ];
 
 /// The unsupported format an id or extension (any case, leading dot allowed) names.

crates/engine/src/cmd/fileio/tests_dxf.rs

@@ -169,7 +169,7 @@ fn formats_list_dxf_and_what_can_not_be_written() {
     }
     assert!(r["writable"].as_array().unwrap().contains(&json!("dxf")));
     let unsupported: Vec<&str> = r["unsupported"].as_array().unwrap().iter().map(|u| u["id"].as_str().unwrap()).collect();
-    assert_eq!(unsupported, ["dwg", "pict"]);
+    assert_eq!(unsupported, ["dwg", "pict", "pmd"]);
 }
 
 #[test]
@@ -191,4 +191,9 @@ fn dwg_and_pict_say_what_to_use_instead() {
         .unwrap_err()
         .to_string();
     assert!(e.contains("DWG is not available"), "{e}");
+    let e = s
+        .execute("document.open", &json!({"name": "brochure.PMD", "dataBase64": vectorcraft_format::base64_encode(b"PageMaker")}))
+        .unwrap_err()
+        .to_string();
+    assert!(e.contains("brochure.PMD") && e.contains("PageMaker"), "{e}");
 }