fix(border-color): keep ComboBox popup clicks inside LeftPanel (TASK 63)

HANDOFF.md

@@ -52,7 +52,8 @@
     (`SceneElement.BorderColorName`, empty for a custom hex), and the hex field keeps a fixed
     width so the name stays next to the hex. The field stays editable (a custom hex can
     still be typed). Guard: `ytLive.Tests/BorderColorNameTests.cs`.
-- **TASK 63 - the border-colour picker IS the app's drop-down** (shipped 2026-10-21). The creator:
+- **TASK 63 - the border-colour picker IS the app's drop-down** (shipped 2026-10-21; **popup click
+  deselection fixed 2026-10-22**). The creator:
   *"why does the drop down under the web cam properties not show the same style for the border
   color drop down list box?"* and *"we established look-and-feel standards. And yet you keep
   ignoring these and I'm wondering why."* **Root cause of the miss:** the TASK 58 sweep looked for
@@ -66,8 +67,17 @@
   `WebcamBorderColorPicker_Click` are **gone**. The closed box != the rows only through
   `Helpers/ClosedBoxTemplateSelector.cs` (WPF copies `ItemTemplate` into the read-only
   `SelectionBoxItemTemplate`; the selector is told them apart by the `ContentPresenter`'s
-  templated parent - `ComboBox` = closed box, `ComboBoxItem` = a row). Guard:
-  `ytLive.Tests/BorderColorPickerTests.cs` (model + panel + the **real widget**). The TASK 60
+  templated parent - `ComboBox` = closed box, `ComboBoxItem` = a row). **2026-10-22 creator bug fix:**
+  clicking a colour in the open `ComboBox` popup registered as an exit from the properties listing
+  because `LeftPanel.IsDescendantOf` used `child is Visual ? VisualTreeHelper.GetParent(child) :
+  LogicalTreeHelper.GetParent(child)` — at `PopupRoot` (which IS a `Visual`),
+  `VisualTreeHelper.GetParent` returns `null`, so `IsDescendantOf` stopped without crossing
+  `PopupRoot`'s logical parent (`PART_Popup` → `ComboBox` → `ElementsScrollViewer`), and
+  `MainWindow.Window_PreviewMouseLeftButtonDown` cleared `SelectedElement = null`. Fixed by falling
+  back to `LogicalTreeHelper.GetParent` / `TemplatedParent` when `VisualTreeHelper.GetParent`
+  returns `null`. Guard: `ytLive.Tests/BorderColorPickerTests.cs` (model + panel + the **real
+  widget**, including `LeftPanel.IsClickInside` on an open popup row and clicking a row to change
+  `BorderColor`). The TASK 60
   guard (`BorderColorPaletteTests`) was updated to guard the new wiring (the drop-down is bound to
   the palette; no second list of colours anywhere).
 - **TASK 55 slice 1 — the log is capped (shipped 2026-10-22).** `startup.log` was uncapped (23 MB
@@ -233,11 +243,10 @@ Zombie entities deleted from the registry: `script.leak_strobe`, `script.doorbel
    the full top area and the circle option is not offered. **PASSES.**
 
 ## Next step
-- **Creator check of TASK 63 (needs the creator's eyes)** — open Live → Layers → webcam →
-  Properties → Border Color: the drop-down must now LOOK like the Display/Font drop-downs (same
-  dark themed chrome, same chevron), the CLOSED box must show the colour's name beside the hex
-  field ("Crimson"), and the open list must show swatch + hex + name. The hex field still accepts a
-  typed colour (the drop-down then shows the swatch with no name — "no name" is the honest answer).
+- **✅ TASK 63 + popup-click fix verified by creator (2026-10-22)** — clicking a colour in the
+  Border Color `YtComboBox` dropdown now stays inside `LeftPanel` (`IsDescendantOf` crosses
+  `PopupRoot` → `PART_Popup` via `LogicalTreeHelper.GetParent`), updates the webcam border colour,
+  and does not exit the properties listing.
 - **Creator check (needs the creator's hands)** — the last piece of the vv feature: switch the
   resolution dropdown to "Vertical 1080p60", confirm the Live camera tile lands inside the band and
   the **Circle** option (TASK 59 turned the Shape button into a Rect | Circle choice) turns the tile