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

Summary

Update `` to implement the PatternFly v6 Switch component.

Toggle switch for binary on/off choices with label support.

Prior Art

Notes

• Implement as a Form-Associated Custom Element (FACE) using `ElementInternals`
• Use ARIA IDL attributes for cross-root ARIA (Baseline 2025)

Requirements

• MUST implement PFv6 visual designs
• MUST provide end-user feature parity with `@patternfly/react-core` Switch
• MUST participate in native form submission via FACE
• 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 `label`, `labelOff` - visible text beside toggle; `label` also used as `aria-label` fallback
• React `isChecked` (controlled) - reflect as `checked` attribute; default via `defaultChecked`
• React `isReversed` - places label before toggle; map to `reversed` attribute
• React `isDisabled` - `ElementInternals` should propagate disabled to form
• React `hasCheckIcon` - shows checkmark inside toggle when on; verify v6 still has this
• `name`/`value` attributes required for form submission

Checklist

Rename

• Delete `elements/pf-v5-switch/`
• 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
• `formAssociated = true` and `ElementInternals` for form participation
• Form submission tested (`name`/`value` submitted when checked)

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
• Form submission test

Reviews

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

Ship

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