fix(release): publish VS Code extension as stable by default

[abdushakoor12]

TLDR

Publish tagged VS Code extension releases as stable by default instead of pre-release.

Details

• Removes the --pre-release flag from the VSIX packaging step in .github/workflows/release.yml.
• Removes the --prerelease flag from GitHub release creation so tagged releases are no longer labeled prerelease by default.
• No runtime or package code changes.

How Do The Automated Tests Prove It Works?

• make ci passed end-to-end after rerunning outside the sandbox.
• The run completed formatting, typechecking, lint, package tests, Playwright web E2E, merged coverage checks, coverage threshold enforcement, and build steps.