fix: preserve rotation logs during quit fallback

Route synchronous account-rotation shutdown flushes through the internal log writer so failures under userData/logs retry userData/internal-logs in the same order as runtime writes.

Keep buffered lines until a target accepts the full chunk, report the successful fallback as the active path, and retain the buffer when every internal target fails.

Cover the real EISDIR primary-path case, complete fallback failure, and main-process quit delegation without launching Electron.

lib/upload-audit.js

@@ -42,7 +42,7 @@ function createInternalLogWriter(options) {
   const maxBackups = Number.isFinite(source.maxBackups) ? source.maxBackups : 2;
   let activePath = null;
 
-  if (!fs || !fs.promises || typeof fs.promises.appendFile !== 'function' || typeof resolveInternalLogPath !== 'function' || typeof fileName !== 'string') {
+  if (!fs || !fs.promises || typeof fs.promises.appendFile !== 'function' || typeof fs.appendFileSync !== 'function' || typeof resolveInternalLogPath !== 'function' || typeof fileName !== 'string') {
     throw new TypeError('createInternalLogWriter requires fs, fileName and resolveInternalLogPath');
   }
 
@@ -66,8 +66,36 @@ function createInternalLogWriter(options) {
     return false;
   }
 
+  function appendSync(line, label) {
+    const excludedPaths = new Set();
+    for (let attempt = 0; attempt < retryDelays.length; attempt++) {
+      const targetPath = resolveInternalLogPath(fileName, excludedPaths);
+      if (!targetPath) break;
+      excludedPaths.add(targetPath);
+      try {
+        fs.mkdirSync(path.dirname(targetPath), { recursive: true });
+        rotateLogFile(targetPath, maxBytes, maxBackups);
+        fs.appendFileSync(targetPath, line, 'utf-8');
+        activePath = targetPath;
+        return true;
+      } catch (error) {
+        reportError(label, error);
+      }
+    }
+    return false;
+  }
+
+  function flushSync(buffer, label) {
+    if (!Array.isArray(buffer) || buffer.length === 0) return true;
+    if (!appendSync(buffer.join(''), label)) return false;
+    buffer.length = 0;
+    return true;
+  }
+
   return {
     append,
+    appendSync,
+    flushSync,
     getActivePath: () => activePath,
     getPath: () => activePath || resolveInternalLogPath(fileName)
   };