[feat]: Update `<pf-v6-icon>` for PatternFly v6

Summary

Update `` to implement the PatternFly v6 Icon component.

Decorative or semantic icon display with size, color, and status variants. Supports inline and standalone usage.

Prior Art

Requirements

• MUST implement PFv6 visual designs
• MUST provide end-user feature parity with `@patternfly/react-core` Icon
• 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

• Port early - used by many other elements (button, alert, label, progress-stepper, etc.)
• React `size`: `sm`, `md`, `lg`, `xl` plus status sizes
• React `color`: `default`, `blue`, `green`, `orange`, `red`, `purple`, `cyan`, `gold`
• React `status`: `custom`, `danger`, `info`, `success`, `warning` - drives color + aria
• React `isInline` - controls `display: inline` vs `inline-block`
• React `progress` prop wraps a Spinner inside the Icon - verify if still in v6
• Async icon loading (network fetch) must not block render; show slot/fallback during load
• `aria-hidden="true"` when decorative; surface `aria-label` for semantic usage

Checklist

Rename

• Delete `elements/pf-v5-icon/`
• Update `elements/package.json` exports
• Update `eslint.config.js` ignore globs if applicable
• Update docs `_snippets/` and `framework-integration/` references

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`)