fix: decode URI-encoded paths when opening local files

Markdown-it percent-encodes non-ASCII characters in link hrefs (e.g.
Chinese/Japanese/Korean filenames). The openFile handler passed these
encoded paths directly to Utils.joinPath, resulting in file-not-found
errors.

Apply decodeURIComponent before constructing the file URI.

Fixes markmap#73

Author: BoosterY

src/extension.ts

@@ -318,7 +318,8 @@ class MarkmapEditor implements CustomTextEditorProvider {
         await writeFile(targetUri, data.content);
       },
       openFile(relPath: string) {
-        const filePath = Utils.joinPath(Utils.dirname(document.uri), relPath);
+        const decoded = decodeURIComponent(relPath);
+        const filePath = Utils.joinPath(Utils.dirname(document.uri), decoded);
         commands.executeCommand('vscode.open', filePath);
       },
       async setFocus(line: number) {