fix(bar): anchor menu panel to top and stop full-screen sizing (#1530)

The dropdown height defaulted to screenCap before the content was measured,
and the ScrollView frame had no alignment, so an unmeasured panel rendered at
nearly full screen height with the content centered in it (macOS then centered
the oversized window). Default to a modest height until measured and pin the
frame to .top, so the popover anchors under the menu bar and sizes to its
content, scrolling only on genuine overflow.

macos-bar/Sources/CCSBarApp/BarMenuView.swift

@@ -51,8 +51,12 @@ struct BarMenuView: View {
   /// Content shorter than the cap renders FULLY with no scroll bar.
   /// Content taller than the cap scrolls.
   private var scrollAreaHeight: CGFloat {
-    guard contentHeight > 0 else { return screenCap }
-    return min(contentHeight, screenCap)
+    let cap = screenCap
+    // Before the first measurement, use a modest default so the popover is never
+    // sized to the full screen (which macOS then centers). Once the content is
+    // measured, use its height, capped.
+    guard contentHeight > 0 else { return min(cap, 560) }
+    return min(contentHeight, cap)
   }
 
   var body: some View {
@@ -132,7 +136,7 @@ struct BarMenuView: View {
         // Content shorter than the cap renders FULLY (no empty space, no clip).
         // Content taller scrolls. contentHeight starts at 0 so we show screenCap
         // until the first preference fires.
-        .frame(height: scrollAreaHeight)
+        .frame(height: scrollAreaHeight, alignment: .top)
         .onPreferenceChange(ContentHeightKey.self) { measured in
           // Only grow, never shrink — prevents a feedback loop where a smaller
           // frame triggers a re-layout that reports an even smaller height.