fix(hud): keep the bar in place across a vertical↔horizontal flip

src/components/launch/LaunchWindow.test.tsx

@@ -1358,9 +1358,19 @@ describe("LaunchWindow overlay sizing", () => {
 		stubBox(bar.parentElement as HTMLElement, 400, stackHeight);
 		await flushResizeObservers();
 
+		// The stub sits at (0, 0), which is not where the stack is in the allocated
+		// window. The reported position must come from the allocation, not the
+		// measurement: a measured one can belong to a viewport the main process has
+		// already resized, and anchoring the next layout flip on it walks the bar (#951).
+		const sizeCalls = (
+			window.electronAPI.setHudOverlaySize as unknown as {
+				mock: { calls: [number, number, unknown][] };
+			}
+		).mock.calls;
+		const [allocatedWidth, allocatedHeight] = sizeCalls[sizeCalls.length - 1];
 		expect(window.electronAPI.setHudOverlayContent).toHaveBeenLastCalledWith({
-			x: 0,
-			y: 0,
+			x: (allocatedWidth - 400) / 2,
+			y: allocatedHeight - HUD_BAR_BOTTOM - stackHeight,
 			width: 400,
 			height: stackHeight,
 		});

src/components/launch/LaunchWindow.tsx

@@ -459,18 +459,18 @@ export function LaunchWindow() {
 		const stackRect = anchorRect?.width && anchorRect.height ? anchorRect : barRect;
 		const stackWidth = stackRect.width || barWidth;
 		const stackHeight = stackRect.height || barHeight;
-		const currentContent = {
-			x: stackRect.x,
-			y: stackRect.y,
+		const contentFor = (size: { width: number; height: number }) => ({
+			x: (size.width - stackWidth) / 2,
+			y: size.height - HUD_BAR_BOTTOM - stackHeight,
 			width: stackWidth,
 			height: stackHeight,
-		};
-		const grantedContent = {
-			x: (granted.width - stackWidth) / 2,
-			y: granted.height - HUD_BAR_BOTTOM - stackHeight,
-			width: stackWidth,
-			height: stackHeight,
-		};
+		});
+		// Computed from the allocation too, never read off stackRect: right after a
+		// resize the observer fires while the old viewport is still laid out, and a
+		// measured position would hand the main process a rect from a window it has
+		// already replaced — the next flip then anchors on it and walks the bar (#951).
+		const currentContent = contentFor(allocated);
+		const grantedContent = contentFor(granted);
 
 		if (!needsResize) {
 			const last = lastSentHudContentRef.current;