[windows-integration] Update stale SHA-pinned actions in windows-cli-integration.yml to match repository conventions

The workflow at `.github/workflows/windows-cli-integration.yml` uses outdated SHA pins for two GitHub Actions that are out of sync with the rest of the hand-written (non-compiled) workflows in this repository.

## Required changes

| Action | Current pin | Current version | Repo-standard pin | Repo-standard version |
|---|---|---|---|---|
| `actions/checkout` | `de0fac2e4500dabe0009e67214ff5f5447ce83dd` | v6.0.2 | `df4cb1c069e1874edd31b4311f1884172cec0e10` | v6.0.3 |
| `actions/setup-go` | `4dc6199c7b1a012772edbd06daecab0f50c9053c` | v6 | `4a3601121dd01d1626a1e23e37211e3254c1c06c` | v6.4.0 |

Both the `build` and `integration` jobs use `actions/checkout`, so there are **two** instances to update.

## Acceptance criteria

- `actions/checkout` in both `build` and `integration` jobs updated to `df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3`
- `actions/setup-go` in the `build` job updated to `4a3601121dd01d1626a1e23e37211e3254c1c06c # v6.4.0`
- All other workflow behavior (triggers, jobs, scenario matrix, chaos tests, hang detection, conclusion job) remains unchanged

## Evidence

Other non-lock workflows such as `agentics-maintenance.yml` consistently use the repo-standard pins listed above. The `upload-artifact` and `download-artifact` pins (v4) are already aligned with the repo convention and do not need to change.

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Open .github/workflows/windows-cli-integration.yml and inspect the checkout steps in the build and integration jobs plus the setup-go step in build. Update only the three specified SHA pins and version comments, then review the diff to confirm triggers, job configuration, matrices, tests, and conclusion behavior are unchanged.

Written by the indexing model from the issue text.