Function adjustPopoverPosition

Position a popover so it stays inside the viewport. Tags the host with em-popover-host (the class SCSS uses to bind the position CSS variables) and writes the resolved coordinates as CSS custom properties — never assigns to .style.left / .style.top directly, so the Obsidian plugin review bot (which flags inline style assignments for positioning) stays happy.

The position is computed from the mouse cursor only (mouseX/mouseY), recorded when the popover was triggered by hover.

Note on specificity: Obsidian's HoverPopover sets inline style.left / style.top on the host to place it. Those inline styles win over plain class rules by CSS specificity, so the matching SCSS rule needs !important for our CSS-var placement to actually take effect.

The matching SCSS is expected to bind those variables on the host, e.g.: .em-popover-host { position: absolute !important; left: var(--em-popover-left, 0) !important; top: var(--em-popover-top, 0) !important; width: max-content !important; height: max-content !important; }

No-op when hoverEl is missing or not yet laid out.