feat: Scaffold the language-service workspace package #289

Description

Language service spike: #209

Create packages/language-service (@openworkflowspec/language-service) to host Open workflow-specific authoring assistance - schema-driven completions and diagnostics.

This package is React-free and Monaco-free by design.

JSON and YAML below will be implemented in separate tickets

@openworkflowspec/language-service
├─ @volar/language-service
│
├─ volar-service-json
│  └─ vscode-json-languageservice
│
├─ volar-service-yaml
│  └─ yaml-language-server
│     └─ yaml
│
└─ OWS-specific language service plugin

Motivation

That is the whole reason it exists as a separate package: the VS Code extension, and later IntelliJ must be able to consume the language service without pulling in Monaco or the React diagram.

Proposed Implementation

No response

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.