add go work verification step for github actions

[koba1t]

This pull request introduces a new job to the GitHub Actions workflow for checking synchronized Go modules.

New job addition:

• .github/workflows/go.yml: Added a check-modules job to ensure Go modules are synchronized. This job checks out the code, sets up Go, runs make workspace-sync, and verifies there are no changes with git diff --exit-code.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: koba1t / name: yugo kobayashi (05cfc90, d8fd502, 67115be)

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[stormqueen1990]

/lgtm

Thanks for adding this!