fix: use block release validation command

[intel352]

Follow-up for GoCodeAlone/workflow#760.

Fixes the release workflow YAML quoting introduced while hardening tag handling:

• converts the pre-build validate-contract command to a block run step
• keeps the shell-level quotes around github.ref_name

Verification:

• git diff --check

[Copilot]

Pull request overview

This PR fixes quoting/escaping issues in the GitHub Actions release workflow by switching the pre-build wfctl plugin validate-contract invocation to a block run step, while preserving safe shell-level quoting around github.ref_name.

Changes:

• Convert the pre-build validate-contract --for-publish command from a single quoted YAML string to a run: | block.
• Keep --tag "${{ github.ref_name }}" shell quoting to avoid tag parsing issues.

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