fix(renderer): add ensureEditor fallback and fix pandoc export path

1. Source editor blank: Added ensureEditor() method with try-catch that
   lazily creates the CodeMirror editor when setEditorContent is called
   if the initial DOMContentLoaded creation failed or was skipped.
   Replaced inline createEditor calls in createTabElements and
   DOMContentLoaded with ensureEditor().

2. Export via pandoc failing: runPandocCmd parsed the full path
   /bin/linux/pandoc as the command, then prepended it to args because
   parsed.command !== 'pandoc'. This caused pandoc to receive its own
   binary path as the first input file. Fix: use path.basename() to
   check if the command ends with 'pandoc' (or 'pandoc.exe').

Amit Haridas

src/main.js

@@ -242,7 +242,9 @@ function runPandoc(args, callback) {
 function runPandocCmd(cmdString, callback) {
   const parsed = parseCommand(cmdString);
   // Skip 'pandoc' if it's the first element (command itself)
-  const args = parsed.command === 'pandoc' ? parsed.args : [parsed.command, ...parsed.args];
+  // Use path.basename to handle full paths like bin/linux/pandoc
+  const cmdBase = path.basename(parsed.command).replace(/\.exe$/i, '');
+  const args = cmdBase === 'pandoc' ? parsed.args : [parsed.command, ...parsed.args];
   const pandocPath = getPandocPath();
   execFile(pandocPath, args, { maxBuffer: 10 * 1024 * 1024 }, callback);
 }