refactor(main): extract file ops to src/main/files/ (search, git, binary)

src/main/files/binary.js

@@ -0,0 +1,13 @@
+// src/main/files/binary.js
+// Binary file write handler (used by Word .docx export)
+const { ipcMain } = require('electron');
+const fs = require('fs').promises;
+
+function register() {
+  ipcMain.handle('write-buffer', async (_event, { path: filePath, buffer }) => {
+    await fs.writeFile(filePath, Buffer.from(buffer));
+    return { ok: true };
+  });
+}
+
+module.exports = { register };