Fix: revalidate workflow fields on external changes (Ctrl+Z)

[lmac-1]

Description

When Y.Doc updates a field value (e.g., via undo/redo or collaborative edits), trigger validation to clear stale errors. This fixes the issue where pressing Ctrl+Z to restore a valid value didn't clear the validation error message.

Previously, field values updated but validation state persisted, leaving error messages visible even when values became valid again.

Addresses point 2 of #4138

Validation steps

1. Type something in the workflow name field in workflow settings panel in collab editor
2. Click Cmd + delete to delete all text from that field (or windows equivalent)
3. Click Save
4. Validation message should appear saying that the field shouldn't be blank
5. Click Ctrl Z on your keyboard so that the previous workflow name is put back
6. Validation message should disappear as the field is now valid AND settings icon in header should be grey (valid).

You can also test this in reverse -> ie using Ctrl + Z to make it so that field is blank to make sure the validation message appears + settings icon is red.

Additional notes for the reviewer

n/a

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Pre-submission checklist

• I have performed a self-review of my code.
• I have implemented and tested all related authorization policies. (e.g., :owner, :admin, :editor, :viewer)
• I have updated the changelog.
• I have ticked a box in "AI usage" in this PR

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.02%. Comparing base (96f7ef9) to head (ab97228).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4157   +/-   ##
=======================================
  Coverage   89.02%   89.02%           
=======================================
  Files         425      425           
  Lines       19605    19605           
=======================================
+ Hits        17453    17454    +1     
+ Misses       2152     2151    -1     

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[doc-han]

Just created an issue that defines this. updating the changelog

[lmac-1]

Thansk @doc-han, much more organised! And thanks @midigofrank for the review.