fix(ui): match spellbook frame and tab alignment

docs/research/2026-07-15-retail-magic-ui-and-casting-pseudocode.md

@@ -221,6 +221,16 @@ UIElement_Text::OnSetAttribute @ 0x0046A640
         SetOneLine(value)
     // absent 0x20 therefore remains multi-line; do not force it true
 
+UIElement_Text::CalcJustification @ 0x00467260
+    available = max(scrollableExtent, surfaceExtent) - leadingMargin - trailingMargin
+    if justification is Center:
+        offset = available / 2 - contentExtent / 2
+    else if justification is Right or Bottom:
+        offset = available - contentExtent
+    else:
+        offset = 0
+    return leadingMargin + offset
+
 UIElement::SetState @ 0x00464E70
     next = desc.AccessStateDesc(stateId)
     if next != current:
@@ -245,6 +255,12 @@ before its retained children lets the center chrome overpaint the caption.
 This rule is derived structurally from `PassToChildren`, not from the two
 spellbook element ids.
 
+Layout `0x21000034` supplies the 300 by 600 content surface, including its tab
+bar and close control, but not the enclosing movable-window border. Production
+mounts it through the same shared retained nine-slice frame used by the
+Attributes/Skills window (`0x2100002E`). Treating the root as already framed
+removes the gold outer border.
+
 The Magic-combat favorite tab captions are authored text (`I` through `VIII`)
 and intentionally omit property `0x20`. Their small rectangles still render
 because retail begins with zero text margins. A generic four-pixel inset on