Fix workflow library unsupported badge

[JPPhoto]

Summary

Fixes Workflow Library callability messaging after Call Saved Workflow support landed. The prior work created too much output noise in the Workflow Library by surfacing negative sub-workflow compatibility state on ordinary workflows. This PR removes that negative badge from the general library view and adds a positive Callable badge only when a workflow can be called by another workflow (i.e. it has a Workflow Return node).

Fixed callable workflow graph validation so saved optional inputs without explicit values use invocation defaults instead of being coerced to None.

Also fixed call-saved-workflow dynamic inputs to automatically resync when a selected child workflow's exposed fields change, preventing stale caller workflows from showing missing-field errors.

Related Issues / Discussions

QA Instructions

• Open the Workflow Library.
• Confirm ordinary workflows without a Workflow Return node do not show Unsupported.
• Confirm workflows that can be used by Call Saved Workflow show a Callable badge.
• Confirm the Call Saved Workflow node picker still disables non-callable workflows and displays the detailed reason there.

Merge Plan

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• ❗Changes to a redux slice have a corresponding migration
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)

[JPPhoto]

I'm still working on the resync behavior - the UI is not forcing a refresh of external fields in the Call Saved Workflow node when switching workflows.