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

Summary

Update `` to implement the PatternFly v6 Label component.

Compact tag for categorization, status, or metadata display. Supports filled/outlined variants, colors, icons, close button, and editable text. Replaces the deprecated Chip component in v6.

Prior Art

Requirements

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

• Label replaces Chip in v6 - no separate `pf-v6-chip` element; Label handles all chip/tag use cases
• React `color`: `blue`, `cyan`, `green`, `orange`, `purple`, `red`, `gold`, `teal`, `grey` (and `white` in some versions) - map to `color` attribute
• React `variant`: `outline`, `filled` - map to `variant` attribute
• React `isCompact` - smaller padding; map to `compact` attribute
• React `isOverflowLabel` - special style for "+N more" overflow labels; map to `overflow` attribute
• React `href` - renders label as ``; surface as attribute, switch inner element accordingly
• React `onClose` - shows close button (X); emit `close` event; close button needs accessible label
• React `isTruncated` - truncates text with ellipsis + tooltip; integrates with ``
• React `textMaxWidth` - max width before truncation kicks in
• React `isEditable`, `editableProps` - inline editable label; complex interaction pattern; verify v6 scope

Checklist

Rename

• Delete `elements/pf-v5-label/`
• 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`)