Add workflow relation metadata to directory items

[daryllimyt]

Summary

• populate workflow directory items with parent/subflow relations derived from subflow execution actions
• expose relation fields through API/client schemas and render them in the workflows dashboard table

Testing

• not run (not requested)

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Codex Task

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Summary by cubic

Adds parent and subflow relations to workflow directory items and displays them in the dashboard with badges linking to related workflows. Improves visibility of workflow dependencies.

• New Features
  • Populate parents/subflows by parsing core.workflow.execute actions (via workflow_alias or workflow_id).
  • Add WorkflowRelationRead and parents/subflows to WorkflowDirectoryItem in API and generated client types.
  • Show a “Relations” column in the workflows table with Parent/Subflow badges that link to the target workflow (alias/title fallback to short ID).

^{Written for commit 218450a. Summary will update automatically on new commits.}