fix(docs): correct mobile copy page menu positioning

[d1rshan]

Description

Fix the mobile Copy Page menu positioning on docs pages.

This removes the custom empty PopoverAnchor from DocsCopyPage and keeps the mobile menu
on the standard Radix trigger/content path so the popover is positioned relative to the
actual trigger button.

Changes

• removed the unused custom PopoverAnchor from DocsCopyPage
• kept the mobile menu on the default PopoverTrigger + PopoverContent pattern
• adjusted the mobile popover alignment to align="end"
• left desktop DropdownMenu behavior unchanged

Motivation

On mobile, the Copy Page action menu could render in the wrong position because the
component defined a custom popover anchor without anchoring it to a real element.

Removing that anchor fixes the positioning issue at the source while keeping the
implementation aligned with how other Radix menus are structured in the codebase.

Breaking Changes

None.

Screenshots

Device / Browser / Viewport: iPhone/Chrome or Safari/mobile viewport under sm

Before	After

[vercel]

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[Yeom-JinHo]

@d1rshan
Tysm for your contribution.