component(ContextMenu): Add DialogContextMenu with Floating UI submenu support

[dan-rukas]

Context

Introduces DialogContextMenu, a new context menu component in ui-next that replaces the legacy ContextMenu from platform/ui. This component is designed to work with OHIF's UIDialogService and provides modern submenu support using Floating UI.

Changes & Results

• Renders context menus for viewport interactions (e.g., right-click on measurements)
• Supports nested submenus that appear inline on hover
• Automatically repositions submenus when near viewport edges
• Matches ui-next styling (consistent with Radix UI components)

Differences from legacy ui

The legacy ContextMenu component had limitations:

• No built-in submenu support
• Submenus required a "close and reopen" hack (jarring UX)
• Styling inconsistent with ui-next components

Screen.Recording.2025-12-10.at.10.08.38.AM.mp4

How it works with OHIF

User right-clicks measurement
        ↓
ContextMenuController.showContextMenu()
        ↓
Builds menu items via ContextMenuItemsBuilder
        ↓
Gets DialogContextMenu via customizationService.getCustomization('ui.contextMenu')
        ↓
Shows via UIDialogService.show({ content: DialogContextMenu, contentProps: { items, menus, ... } })
        ↓
DialogContextMenu renders at click position

Floating UI integration

Submenus use Floating UI for intelligent positioning:

• offset(4) - Adds 4px gap between parent menu and submenu
• flip() - Flips submenu to opposite side if no room (right → left)
• shift() - Shifts submenu along axis to stay in viewport

This ensures submenus are always visible regardless of where the user clicks.

Key changes

File	Change
DialogContextMenu.tsx	New component with Floating UI submenu support
ContextMenuController.tsx	Commented out legacy onShowSubMenu callback (no longer needed)
contextMenuUICustomization.ts	Registers DialogContextMenu as 'ui.contextMenu'

Testing

• Right-click on measurement → menu appears at click position
• Hover over submenu item → submenu appears inline
• Click near screen edge → submenu flips/shifts to stay visible
• Click menu item → action executes, menu closes

Checklist

PR

• My Pull Request title is descriptive, accurate and follows the
  semantic-release format and guidelines.

Code

• My code has been well-documented (function documentation, inline comments,
  etc.)

Public Documentation Updates

• [] The documentation page has been updated as necessary for any public API
  additions or removals.

Tested Environment

• OS: macOS Sequoia 15.7.1 (24G231), Apple M4 Pro
• Node version: 20.19.1
• Browser: Chrome 143.0.7499.41 (Official Build) (arm64)

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[sedghi]

Could you please reach out to Bill about adding a customization to retain the old context menu for the next version? We could call this ui-next.contextMenu to keep it separate, and then remove ui.contextMenu later on.

[sedghi]

we should check which customization is used, either if old one (ui.context-menu) keep this if the new one (default for us) not use this piece of code

[sedghi]

please see my comments

[dan-rukas]

Migrating legacy component before creating a new implementation: #6008