Disable Marketplace publishing in release workflow

[MelbourneDeveloper]

TLDR

Comment out VSIX Marketplace publication and its credential preflight so Marketplace access cannot block NuGet releases.

What Was Changed or Deleted?

• Comment out the release workflow’s Marketplace authentication step and complete publish-vsix job, as requested.
• Remove the unused OIDC permission from prepare.
• Preserve the tagged version stamping, CI and CodeQL gates, and NuGet publishing steps.

How Do The Automated Tests Prove It Works?

• make ci passes on the committed source plus these two scoped changes.
• actionlint .github/workflows/release.yml passes.
• Parsed YAML confirms no active Marketplace preflight or VSIX job; NuGet still depends on CI and CodeQL.
• Pi read-only review found no blockers or dangling dependencies.

Spec / Doc Changes

Update [CI-RELEASE-GATE], [CI-RELEASE-PREFLIGHT], and [SWR-VSIX-PUBLISH-AUTH] to document the disabled Marketplace release path.

Breaking Changes

• None to package APIs. VSIX publication is intentionally disabled.