Check npm registry instead of git diff in release workflow

[Copilot]

Release workflow now checks if a version exists on npm registry instead of checking git commit history for version changes. This prevents publish failures when the version in package.json hasn't changed but also hasn't been published yet.

Changes

• check-version job: Replace git diff HEAD^ HEAD -- package.json check with npm view <package>@<version> registry query
• Job outputs: Changed from version-changed to should-publish boolean
• Release condition: Gate on should-publish == 'true' instead of version-changed == 'true'
• Checkout step: Remove fetch-depth: 2 since git history comparison is no longer needed

Behavior

# Before: checked git commits
if git diff HEAD^ HEAD -- package.json | grep -q '"version"'; then
  publish  # Could fail if version already on npm
fi

# After: checks npm registry
if npm view "$PACKAGE_NAME@$VERSION" version 2>/dev/null; then
  skip  # Version already published
else
  publish  # Proceed with release
fi

The workflow now exits gracefully when attempting to publish an existing version rather than failing at the npm publish step.

Original prompt

Change the release workflow. it should not only run when the given version number has been changed. instead, check whether the version number has already been published to npm. if it has exit. If it has not, continue to publish.

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