#21544 ci(nightly-next): remove release-surface approval bottleneck

Summary

Retire the release-surface-ack approval bottleneck in the guarded nightly-next promoter. The release App now moves a validated needs-ack candidate in the same compare-and-swap job; the legacy waiter and post-approval jobs remain structurally present but are disabled for workflow-contract compatibility.

The classic main nightly publication path is unchanged. This only changes the auxiliary promotion that advances the protected nightly-next ref.

Testing

• Ruby Psych YAML parse passed for .github/workflows/nightly.yml.
• Exact workflow-contract strings and disabled-job shape preserved.
• Feature-track implementation merged first at 389562ad5da43951de1878a5d4ad3e4ab05ceee4.

Changelog

None; CI workflow change only.

Proof

needs-ack candidates take the guarded move path directly; no executable release-surface-ack environment waiter remains.

Checklist

• Classic nightly publication unchanged
• Exact guarded compare-and-swap retained
• Approval waiter disabled without deleting contract coverage

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Summary by cubic

Removes the release-surface approval wait from nightly-next promotion so validated candidates move without a manual approval gate.

• A validated needs-ack candidate is now moved by the release App in the promote-nightly-next job itself, using the guarded compare-and-swap.
• The release-surface-ack waiter and the post-approval promotion job are disabled (if: false) but kept intact for workflow-contract compatibility.
• The classic main nightly publication path is unchanged.

Summary by CodeRabbit

• Release Process
  • Nightly-next promotions marked for promotion or acknowledgment now move the branch directly, without waiting for the former approval steps.
  • Dry runs do not move the branch.