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

[bennypowers]

Summary

Update <pf-v6-badge> to implement the PatternFly v6 Badge component.

Numeric count indicator, typically used to show unread items or notification counts.

Prior Art

Source	Element	Status
PFE v4	<pf-badge>	Exists
cem	<pf-v6-badge>	Exists
cockpit	<pf-v6-badge>	Exists
chickadee	--	--

Requirements

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