feat(CT6): character window Y-resize clamped at retail's authored host minimum + shrink-and-scroll list contract

CT6 (Campaign CT slice 6): the resize clamp source is the SHARED
gmPanelUI host (0x100005FE in LayoutDesc 0x2100006E), not 0x2100002E's
own root and not the Character/Skills slot 0x1000018E either — live
probe confirmed the host authors MinWidth=MaxWidth=310 (fixed — no
horizontal Resizebar authored), MinHeight=372, MaxHeight=1000, and that
the bottom Resizebar (0x10000660) and top Dragbar (0x1000065C) are
direct children of the host, not the content parent. Decomp chain:
UIElement_Resizebar::StartMouseResizing @0x0046B7E0 calls
UIElement::StartResizing(this->GetParent(), ...), stashing drag state on
that parent; UIElement::MouseResizeElement @0x00461130 then reads
GetAttribute_Int(this, 0x3C..0x3F) off that same element every
mouse-move.

RetailUiRuntime.MountCharacter now imports the host element and passes
it as RetailWindowFrame.Options.DatConstraintSource, matching the
existing MountSideVitals pattern.

CharacterStatController.RebuildActiveList now wraps BOTH the Attributes
and Skills tabs' rows in the same UiScrollablePanel viewport (previously
only Skills got one; Attributes rows had no clipping/scrolling and the
shared scrollbar was force-hidden — owner report item 2). The shared
scrollbar is now always bound + visible; UiScrollbar's own
IsPresentationVisible/IsModelDisabled already draw the correct
full-track "disabled" thumb when content fits. This surfaced and fixed
a real #372/#412-class anchor-baseline bug: the viewport's
Left|Top|Bottom anchor was capturing its baseline margins lazily on its
own first ApplyAnchor call, which happens AFTER the ListBox has already
grown from its raw DAT height to its mounted height, permanently
capping the viewport short on every later resize. Fixed with an eager
CaptureCurrentAnchorBaseline() call, mirroring UiTemplateListBox
.Viewport's own lazy getter.

CharacterTitlesController.Bind gained the same defensive
Anchors = Left|Top|Bottom fallback for the Titles ListBox that
CharacterStatController already had (a no-op on the real DAT — both the
Titles page and its ListBox already carry a real authored LayoutPolicy
that stretches correctly).

Standardization audit: UiElement.MinWidth/MinHeight/MaxWidth/MaxHeight,
set once at RetailWindowFrame.Mount, are the ONLY clamp fields — read
identically by interactive drag, RetailWindowManager.ResizeTo, and
RetailWindowLayoutPersistence's restore clamp. No gaps found; no
register row (every number is a live-probed authored DAT value or a
structural correctness fix, nothing inferred).

Tests: CharacterStatControllerTests
.CharacterWindow_ResizesYWithinAuthoredHostClamp_AndReflowsListAndScrollbar,
CharacterTitlesControllerTests
.TitlesList_ReflowsWithWindowResize_AndScrollbarOverflowFlips,
RetailWindowFrameTests
.NineSlice_ChatShapedConstraints_ClampProgrammaticResizeAtAuthoredBounds
(shared-mechanism regression pin), CharacterPanelLiveDatTests
.PanelHost_AuthorsFixedWidthAndBottomOnlyResizeContract (InstalledDat
pin). Existing attribute-row tests updated from list.Children to
Descendants(list) for the new nested-viewport shape (the pattern skill
rows already needed).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/research/2026-08-25-campaign-ct-test-script.md

@@ -73,13 +73,53 @@ Useful ACE console helpers: title grants come from quests/admin — check
 
 ## 4. Resize + scrollbar (CT6)
 
-*(Section finalized after CT6 lands — placeholder items below.)*
+Ground truth (2026-08-25 live probe against layout `0x2100006E`, host
+`0x100005FE` — `docs/research/2026-08-24-campaign-ct-dat-ground-truth.md`
+§CT6): the resize clamp is authored on the SHARED `gmPanelUI` host, not
+the character content itself. Host authors **MinWidth=MaxWidth=310**
+(fixed width — no horizontal Resizebar) and **MinHeight=372,
+MaxHeight=1000**. With the NineSlice chrome's 10px inset, the MOUNTED
+window's outer bounds are MinHeight≈382px, MaxHeight≈1010px, width
+fixed ≈320px.
 
-1. Resize the character window vertically: it clamps at the authored
-   minimum; the stat list shows its scrollbar when the shortened
-   viewport overflows, with retail hover/press states on the bar.
-2. Other windows (chat, social) still clamp at their own authored
-   minimums — regression check.
+1. **Grab the bottom edge and drag up (shrink).** PASS: the window
+   stops shrinking at its authored floor (≈382px outer / the point where
+   further dragging has no visible effect) — it does NOT collapse
+   arbitrarily small, and it does NOT refuse to shrink at all (the
+   pre-CT6 bug). Retail comparison: drag retail's own Character/Skills
+   window to its floor side-by-side; both should bottom out at
+   proportionally the same point relative to their starting size.
+2. **Keep dragging down (grow).** PASS: the window keeps growing until
+   its authored ceiling (≈1010px outer) — same side-by-side comparison
+   against retail's own ceiling.
+3. **Left/right edges do not resize.** Only the bottom edge (and top
+   Dragbar for moving, not resizing) responds — matches retail's
+   fixed-width authoring (no horizontal Resizebar).
+4. **Scrollbar hand-off, Attributes tab.** At the default window size
+   the 9 attribute/vital rows fit without a visible scroll gap (bar
+   shows retail's full-track "disabled" thumb — present, not hidden,
+   per the 2026-08-24 scrollbar work's contract). Shrink the window
+   until the rows overflow: the bar's thumb shrinks proportionally and
+   becomes interactive (drag, click-to-page, wheel-scroll all move the
+   list). PASS: this is the owner's item 2 fix — previously the
+   scrollbar never appeared on Attributes at all.
+5. **Scrollbar hand-off, Skills tab.** Same shrink/overflow check —
+   should already have worked pre-CT6; confirm no regression.
+6. **Scrollbar hand-off, Titles tab.** With several earned titles,
+   shrink the window until the Titles list (authored 455px, inside the
+   575px page) overflows its available space — the list's own scrollbar
+   (`0x10000533`) takes over the same way.
+7. **Footer stays bottom-docked.** While shrinking/growing on the
+   Attributes/Skills tabs, the footer (raise buttons / selected-stat
+   info) stays pinned to the bottom edge — it does not float mid-window
+   or get clipped early.
+8. **Grow back restores.** Drag back to the original size: the lists
+   return to showing all rows without scrolling (scrollbar reverts to
+   the full-track disabled state) and the window returns to its
+   original proportions.
+9. Other windows (chat, social) still clamp at their own authored
+   minimums — regression check (chat: min 300×100, max 2000×2000 per
+   `CharacterPanelLiveDatTests.ChatWindowRoot_AuthorsExplicitSizeConstraints`).
 
 ## 5. Regression sweep (5 minutes)