fix: export run() to avoid Windows spawnSync issues (#431)

- session-end-marker.js now exports run() function
- Enables in-process execution via run-with-flags.js
- Avoids spawnSync cross-platform issues on Windows
- Maintains backward compatibility with direct CLI execution

Fixes #429

Co-authored-by: 阳虎 <yanghu@yanghudeMacBook-Pro.local>

scripts/hooks/session-end-marker.js

@@ -1,6 +1,17 @@
 #!/usr/bin/env node
 'use strict';
 
+/**
+ * Session end marker hook - outputs stdin to stdout unchanged.
+ * Exports run() for in-process execution (avoids spawnSync issues on Windows).
+ */
+
+function run(rawInput) {
+  return rawInput || '';
+}
+
+// Legacy CLI execution (when run directly)
+if (require.main === module) {
   const MAX_STDIN = 1024 * 1024;
   let raw = '';
   process.stdin.setEncoding('utf8');
@@ -13,3 +24,6 @@ process.stdin.on('data', chunk => {
   process.stdin.on('end', () => {
     process.stdout.write(raw);
   });
+}
+
+module.exports = { run };