feat: Publish the language-service package to npm #330

Description

Language service package: #329
Publish @openworkflowspec/language-service to npm and integrate it with the existing release process.

Motivation

Make the language service available to consumers outside the monorepo and enable usage with Web Components.

Proposed Implementation

• Publish @openworkflowspec/language-service initial version to npm
• Configure npm OIDC for the package so the existing GHA release workflow can publish it automatically

Definition of Done

• Implementation: Fully implemented according to the Open Workflow spec.
• Unit Tests: Comprehensive unit tests are included and passing.
• Integration Tests: Verified within the monorepo and target environments (Web/VS Code).
• Documentation: Updated README.md, ADRs, or official docs.
• Performance: No significant regression in editor responsiveness.
• Accessibility: UI changes comply with accessibility standards.