fix: ensure binary is executable after npm install (#229)

.changeset/fix-binary-permissions.md

@@ -0,0 +1,5 @@
+---
+"agent-browser": patch
+---
+
+Fix binary permissions on install. npm doesn't preserve execute bits, so postinstall now ensures the native binary is executable.

scripts/postinstall.js

@@ -68,7 +68,11 @@ async function downloadFile(url, dest) {
 async function main() {
   // Check if binary already exists
   if (existsSync(binaryPath)) {
-    console.log(`✓ Native binary already exists: ${binaryName}`);
+    // Ensure binary is executable (npm doesn't preserve execute bit)
+    if (platform() !== 'win32') {
+      chmodSync(binaryPath, 0o755);
+    }
+    console.log(`✓ Native binary ready: ${binaryName}`);
     return;
   }