MCP: document.inspect and document.open report the File Info title as fileInfoTitle

The title field of document.inspect and the document.open reply is the
document's tab name, which comes from the file name once the document
is saved to or opened from a file. A client had to call file.info or
document.info to read the File Info title, so reading a saved
document's title from these replies gave the file name instead.

Both replies now add fileInfoTitle, the title file.info reports, and
keep title as it was. docs/mcp.md's File Info section describes both.

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

@@ -463,8 +463,12 @@ fn open_loaded(s: &mut Session, loaded: Loaded, links: Resolved, path: Option<St
     st.converted = converted;
     st.imported_from = source_path;
     st.import_losses = losses;
-    let title = s.documents()[index].title();
-    Ok(super::merge(json!({ "index": index, "title": title, "format": format.id, "warnings": warnings, "restored": restored }), links.to_json()))
+    let opened = &s.documents()[index];
+    let (title, file_info_title) = (opened.title(), opened.doc.title.clone());
+    Ok(super::merge(
+        json!({ "index": index, "title": title, "fileInfoTitle": file_info_title, "format": format.id, "warnings": warnings, "restored": restored }),
+        links.to_json(),
+    ))
 }
 
 /// A file named by a command's params: `{path}` (read from disk) or `{name, dataBase64}`.

crates/engine/src/inspect.rs

@@ -265,6 +265,8 @@ fn document_base(s: &Session) -> Value {
     json!({
         "uid": st.uid,
         "title": st.title(),
+        // The File Info title (`file.info`), where `title` comes from the file name once the document has one.
+        "fileInfoTitle": d.title,
         "path": st.path,
         "dirty": st.is_dirty(),
         "revision": st.revision,

crates/engine/src/tests_fileinfo.rs

@@ -112,6 +112,29 @@ fn saving_to_a_file_stamps_the_modified_date() {
     assert!(s.execute("file.info", &json!({})).unwrap()["modified"].is_string());
 }
 
+#[test]
+fn inspect_and_open_report_the_file_info_title_beside_the_file_name() {
+    let dir = std::env::temp_dir().join(format!("vc-fileinfotitle-{}", std::process::id()));
+    std::fs::create_dir_all(&dir).unwrap();
+    let path = dir.join("poster.vectorcraft");
+    let mut s = session();
+    // Untitled, the two are the same.
+    let r = s.execute("document.inspect", &json!({"depth": 0})).unwrap();
+    assert_eq!((r["title"].as_str(), r["fileInfoTitle"].as_str()), (Some("Poster"), Some("Poster")));
+    s.execute("file.info", &json!({"title": "Poster: final"})).unwrap();
+    s.execute("document.save", &json!({"path": path.to_str().unwrap()})).unwrap();
+    let r = s.execute("document.inspect", &json!({"depth": 0})).unwrap();
+    assert_eq!((r["title"].as_str(), r["fileInfoTitle"].as_str()), (Some("poster.vectorcraft"), Some("Poster: final")));
+    // Opened from the file, in another session.
+    let mut s = Session::new();
+    let opened = s.execute("document.open", &json!({"path": path.to_str().unwrap()})).unwrap();
+    assert_eq!((opened["title"].as_str(), opened["fileInfoTitle"].as_str()), (Some("poster.vectorcraft"), Some("Poster: final")));
+    let r = s.execute("document.inspect", &json!({"depth": 0})).unwrap();
+    assert_eq!((r["title"].as_str(), r["fileInfoTitle"].as_str()), (Some("poster.vectorcraft"), Some("Poster: final")));
+    assert_eq!(r["fileInfoTitle"], s.execute("file.info", &json!({})).unwrap()["title"]);
+    let _ = std::fs::remove_dir_all(dir);
+}
+
 #[test]
 fn pdf_info_carries_author_subject_and_keywords() {
     let mut s = session();