Create Scaffold for the Issue Synchronization Service

This ticket covers the initial setup and scaffolding for the new SyncService, which will be the heart of the bi-directional issue synchronization mechanism. This involves creating the service class itself, exposing it as a new tool, and defining the structure for its state management.

Acceptance Criteria

1. A new file, ai/mcp/server/github-workflow/services/SyncService.mjs, is created.
2. The file defines a new class, SyncService, that extends Neo.core.Base and is configured as a singleton.
3. A placeholder method, runFullSync(), is created within the SyncService.
4. The openapi.yaml for the github-workflow server is updated to include a new sync_issues tool that calls this service.
5. The serviceMapping in ai/mcp/server/github-workflow/services/toolService.mjs is updated to map the sync_issues operationId to SyncService.runFullSync.
6. The SyncService includes #loadMetadata() and #saveMetadata() methods that read from and write to a new .github/.sync-metadata.json file. The initial structure of this JSON file should be defined (e.g., { "last_sync": null, "issues": {} }).

Benefits

• Establishes the core architectural component for the sync process.
• Creates the necessary API endpoint for agents to trigger the synchronization.
• Provides the foundation for stateful, delta-based updates.