[feat]: Create <pf-v6-action-list> element #2977

Summary

Create `` to implement the PatternFly v6 Action list component.

Horizontal group of actions or buttons with consistent spacing and alignment.

Prior Art

Sub-components

• `` - Individual action within the list
• `` - Grouped actions (e.g. separator between primary and cancel actions)

Requirements

• MUST implement PFv6 visual designs
• MUST provide end-user feature parity with `@patternfly/react-core` ActionList
• MAY adjust element API to leverage web platform strengths
• SHOULD maintain CSS custom property theming compatibility
• SHOULD expose useful CSS shadow parts

Element-specific considerations

• React `isIconList` - icon-only buttons with no text; adjusts spacing; map to `icon-list` attribute
• `ActionListGroup` - groups actions; used to visually separate primary actions from cancel/secondary
• Layout only; no interactive behavior on the container itself - it's a flex/grid wrapper
• Children are `` or standard ``/`` elements
• No ARIA roles needed on container beyond standard `
  ` layout

Checklist

Implementation

• API per `.claude/ADVICE.md`
• CSS uses v6 tokens, logical properties, nesting
• `@summary` and JSDoc on element class

Demos

• Demos match patternfly.org naming/structure
• CSS custom properties match computed styles from patternfly.org (Chrome MCP)
• Visual parity verified via Chrome MCP

Tests

• Public API covered (attributes, properties, events, slots)
• `a11ySnapshot` assertions

Reviews

• `/review-api` passes
• `/review-demos` passes
• `/review-a11y` passes
• `eslint` and `stylelint` pass

Ship

• Add changeset
• PR targets `staging/pfv6` (NOT `main`)