Fix runner hook execution by inheriting system environment

The GitHub Actions runner was failing to execute job hooks with
'sh: command not found' error. This was because the runner process
was started with only RUNNER_ALLOW_RUNASROOT in its environment,
missing PATH and other system variables needed to locate and
execute shell commands.

Fixed by inheriting the system environment when starting the runner
process, ensuring PATH and other critical environment variables are
available.

Author: ryan-williams

src/ec2_gha/templates/user-script.sh.templ

@@ -437,8 +437,11 @@ for config in configs:
 
     # Start runner in background (use full path and handle errors)
     try:
+        # Inherit system environment and add RUNNER_ALLOW_RUNASROOT
+        runner_env = os.environ.copy()
+        runner_env['RUNNER_ALLOW_RUNASROOT'] = '1'
         proc = subprocess.Popen([f'{runner_dir}/run.sh'],
-                               env={'RUNNER_ALLOW_RUNASROOT': '1'},
+                               env=runner_env,
                                cwd=runner_dir,
                                stdout=subprocess.DEVNULL,
                                stderr=subprocess.DEVNULL)