Create pf-generate-keyboard-nav-flow skill

[patternfly-jira-sync]

Generates a keyboard navigation spec for complex interactions — focus order, arrow key behavior, escape handling, roving tabindex.

AC:

• Skill exists in a11y plugin

• Produces a structured keyboard nav spec from component code

• Covers tab order, arrow keys, and escape behavior

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Jira Issue: PF-4177