A quoted Editable: '<expression>' on an input widget is silently dropped: the field stays editable #1567

Repro (v0.26.0, current main, and #1564; headerless and with mdl 1;; Mendix 11.12.5)

create persistent entity Shop.Item (Flag: Boolean, Locked: Boolean, Code: String(50));

create or modify page Shop.PRB_Editable
( Title: 'Probe', Layout: Atlas_Core.PopupLayout, Params: { $Item: Shop.Item } )
{
  dataview dvP (DataSource: $Item) {
    layoutgrid lgP { row rowP { column colP (DesktopWidth: AutoFill) {
      checkbox cbQuotedEditable   (Label: 'A', Attribute: Flag, Editable: '$currentObject/Locked = false')
      checkbox cbQuotedVisible    (Label: 'B', Attribute: Flag, Visible:  '$currentObject/Locked = false')
      textbox  tbQuotedEditable   (Label: 'C', Attribute: Code, Editable: '$currentObject/Locked = false')
      checkbox cbUnquotedEditable (Label: 'D', Attribute: Flag, Editable: $currentObject/Locked = false)
    } } }
  }
};

check passes, exec reports Created page, and mx check reports 0 errors. What gets stored:

The quoted Visible: is kept, but the quoted Editable: disappears with no diagnostic. A field meant to be locked becomes editable for everyone, and describe simply omits the property.

Cause

Both keys parse a string literal into the plain property, and the difference is in how each value is consumed:

• Visible goes through pages.StaticVisibleExpression (sdk/pages/pages_widgets.go). Its default branch takes any other non-empty string as the condition.
• Editable (cmd_pages_builder_v3.go, around line 599) only consults pages.CanonicalEditability, which accepts exactly Always, Never or Conditional. Anything else is skipped without a word.
• The check rule MDL-WIDGET19 lets any string through for both keys.

alter page … set (Editable: '…') already refuses the same value, so only the create, replace and insert paths lose it.

Fix

Give Editable the same rule as Visible. A quoted string that is not Always, Never or Conditional is stored as the conditional editability expression, exactly like the unquoted form, and check validates it the same way. I have a PR ready and will link it.

Workaround: write it unquoted: Editable: $currentObject/Locked = false.