Avoid overlapping spotlight tiles with the app bar

The default inset that is given to the fixed layout layer needs to account for the app bar now.

src/room/InCallView.tsx

@@ -516,11 +516,11 @@ export const InCallView: FC<InCallViewProps> = ({
         key="fixed"
         className={styles.fixedGrid}
         style={{
-          insetBlockStart:
-            edgeToEdge || headerBounds.height === 0 ? 0 : headerBounds.bottom,
+          // If not edge-to-edge, consume the header insets right here.
+          insetBlockStart: edgeToEdge ? 0 : bounds.top + headerBounds.height,
           height: edgeToEdge ? "100%" : gridBounds.height,
           // If edge-to-edge, compute new safe area insets that account for the
-          // header and footer.
+          // header and footer, passing them down to the tiles.
           "--call-view-safe-area-inset-top":
             edgeToEdge && headerStyle !== HeaderStyle.None && showHeader
               ? // Header has two relevant cases: if it's an app bar, it lives

src/room/__snapshots__/InCallView.test.tsx.snap

@@ -104,6 +104,7 @@ exports[`InCallView > rendering > renders 1`] = `
     </div>
     <div
       class="fixedGrid grid"
+      style="inset-block-start: NaNpx;"
     >
       <div />
     </div>