Pass socket path from step-runner serve to proxy command

What does this MR do?

Updates the step-runner integration to pass the socket path from the serve command to the proxy command, ensuring they use the same socket for communication.

Changes:

• Modified the ready message to include the socket path: step-runner is listening on socket <path>
• Updated readyWriter to parse and extract the socket path from the ready message
• Pass the extracted socket path to the proxy command via --socket flag
• Upgraded gitlab.com/gitlab-org/step-runner from v0.31.0 to v0.32.0

Why was this MR needed?

Previously, the proxy command did not receive the socket path from the serve command, which could cause connection failures when the socket paths didn't match. This was causing "container is not running" errors in pilot runner jobs.

What's the best way to test this MR?

Run a job using pilot runners and verify that step-runner connections succeed without "container is not running" errors.

What are the relevant issue numbers?

Relates to step-runner#413 (closed)