Add Composite component

[zamoore]

📌 Summary

If merged, this PR adds a new HdsComposite component that provides accessible keyboard navigation (roving tabindex) for composite widget patterns such as toolbars, listboxes, and 2D grids. This will be used as a foundational building block for keyboard navigation in the AdvancedTable component.

🛠️ Detailed description

The Composite component implements the WAI-ARIA Composite keyboard navigation pattern using a modifier-based API. It yields three modifiers via a contextual hash:

• {{c.composite}} - Applied to the container element. Listens for keydown events and manages the composite's tabindex when no item is active.
• {{c.item}} - Applied to each navigable item. Manages roving tabindex (0 for active, 1 for inactive), data-active-item attribute, and aria-disabled. Accepts an optional disabled named argument.
• {{c.group}} - Applied to row/group containers to enable 2D grid navigation.

Supported features:

• @orientation - "horizontal", "vertical", or omitted for both axes. Controls which arrow keys are active.
• @loop - true (all axes), "horizontal", or "vertical". Wraps focus from last to first (or vice versa) within the axis.
• @wrap - true, "horizontal", or "vertical". In 2D grids, overflows navigation into adjacent rows/columns.
• @defaultCurrentId - Pre-selects a specific item or explicitly sets no active item (null`).

2D grid navigation

When groups are present and no @orientation is set, switches to 2D mode with ArrowLeft/ArrowRight within rows, ArrowUp/ArrowDown across rows, Home/End for row edges, Ctrl+Home/Ctrl+End for grid edges, and PageUp/PageDown for column edges.

🔗 External links

Jira ticket: HDS-6131

---

👀 Component checklist

• Percy was checked for any visual regression
• A changelog entry was added via Changesets if needed (see templates here)

💬 Please consider using conventional comments when reviewing this PR.

📋 PCI review checklist

• If applicable, I've documented a plan to revert these changes if they require more than reverting the pull request.
• If applicable, I've worked with GRC to document the impact of any changes to security controls.
  Examples of changes to controls include access controls, encryption, logging, etc.
• If applicable, I've worked with GRC to ensure compliance due to a significant change to the in-scope PCI environment.
  Examples include changes to operating systems, ports, protocols, services, cryptography-related components, PII processing code, etc.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
hds-showcase	Ready	Preview	Mar 4, 2026 2:25am
hds-website	Ready	Preview	Mar 4, 2026 2:25am