[Bug]: Dropdown menu content is misaligned with its trigger button

[asphum]

Component

NavigationMenu

Describe the bug

When opening the dropdown menu, the dropdown panel does not align
with (or anchor to) the trigger button that opens it. The panel
appears offset/detached from the trigger instead of being
positioned directly below (or relative to) it, causing a visual
mismatch between the menu item and its opened content.

Reproduction

1. Render a navbar with multiple menu triggers (e.g. หน้าแรก,
   มีอดีต, โน้ตบุ๊ค, แท็บเล็ต, พีซี, ชิ้นส่วน) using the dropdown
   component
2. Click/hover on one of the trigger buttons (e.g. "ชิ้นส่วน") to
   open its dropdown menu
3. Observe that the dropdown panel is not aligned with the trigger
   button it belongs to

Expected: the dropdown panel should be positioned relative to
(e.g. directly below) the trigger element that opened it.
Actual: the dropdown panel appears misaligned/offset from the
trigger.

sv5ui version

2.7.0

Area

Not sure

Checklist

• I searched existing issues and this is not a duplicate.
• I reproduced this on the latest version of sv5ui.

[ndlabdev]

Thanks for the report and the screenshot. Confirmed.

Cause

A horizontal NavigationMenu shows every dropdown in one shared panel, and that panel was always placed at the left edge of the menu, whichever trigger opened it. With six items, the last trigger opened a panel more than 400px to its left, and with short dropdown content the panel did not even sit under the trigger anymore.

Fix

The panel now opens under the trigger that opened it:

• It is centred on the trigger by default. A new align prop ('start', 'center' or 'end') changes that.
• It stays inside the menu, so it shifts back when the trigger is close to either edge.
• It slides from one trigger to the next, and it follows the menu when the list scrolls horizontally.
• It works with dir="rtl", and on small screens the panel keeps its full width as before.

While fixing this I also removed the 8px gap that the menu always reserved under its items for the scrollbar. That space is now added only when the items overflow and can scroll, so the dropdown sits closer to the menu.

The fix is in #222 and will be part of the next release. If the dropdown is still misaligned after upgrading, please share a runnable reproduction and I will take another look.