Sync workflow-v1.0.json schema with server-side copy

[ericsciple]

Summary

The workflow-parser/src/workflow-v1.0.json schema should be synced with GitHub's server-side workflow schema to ensure validation parity.

Background

The languageservices repo maintains its own copy of the workflow schema. Over time, the server-side schema may have additions or changes that aren't reflected here, leading to:

• False positive validation errors (rejecting valid workflows)
• False negatives (accepting invalid workflows)

Tasks

• Compare workflow-v1.0.json with the server-side schema in actions-workflow-parser
• Identify differences and update accordingly
• Ensure all existing tests still pass
• Add tests for any new schema elements

Related

• PR Add missing activity types for pull_request and pull_request_target #242 added a schema sync test for pull_request activity types
• Consider adding automated sync or diff tooling to catch future drift