fix(web-components): support middle-click to open links in new tab (Fixes #36567)

[water (waterWang)]

Description

fluent-link and fluent-anchor-button did not respond to middle mouse button clicks. The @click event only fires for left-button clicks; middle-click triggers the auxclick event, which was not handled.

When a user middle-clicks a native <a> element, the browser opens the link in a new tab. These components should provide the same behavior.

Changes

1. anchor-button.base.ts: Added auxclickHandler method to BaseAnchor that opens the link in a new tab when the middle mouse button (event.button === 1) is pressed.
2. anchor-button.template.ts: Added @auxclick binding to the template.
3. link.template.ts: Added @auxclick binding to the template (Link extends BaseAnchor, so it inherits the handler).

Testing

• Middle-click on fluent-link with href → opens in new tab
• Middle-click on fluent-anchor-button with href → opens in new tab
• Left-click behavior unchanged
• Ctrl/Cmd+click behavior unchanged
• Right-click context menu unchanged

Fixes #36567

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