Run golangci-lint in runner CI (not just go vet)

[mayankpande88]

The repo ships a runner/.golangci.yml config and the make lint target supports golangci-lint, but the runner CI workflow should actually run golangci-lint rather than only go vet. This catches a much wider class of issues on every PR.

Goal

Ensure golangci-lint runs in CI for the runner using the committed .golangci.yml.

Scope

• Verify whether .github/workflows/runner-lint-test.yaml currently runs golangci-lint. If it only runs go vet, add the official golangci/golangci-lint-action step (pinned version) pointed at the runner/ module.
• Make sure it uses the existing runner/.golangci.yml config.
• Confirm the job passes on the current main (fix or report any newly surfaced lint findings; large fixes can be split into follow-up PRs).

Pointers

• .github/workflows/runner-lint-test.yaml
• runner/.golangci.yml
• runner/Makefile (make lint)

Acceptance

• CI runs golangci-lint on PRs that touch the runner and the check is green on main.