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

Fixes a YAML quoting issue in the release workflow by converting the pre-build validate-contract step into a block-scalar run: command, which avoids the nested-quote parsing problem from the prior single-line form.

Changes:

• Convert the validate-contract step's run: from a quoted single-line string into a run: | block.
• Preserve shell-level quoting around ${{ github.ref_name }} and the wfctl binary path.

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