[feat]: Rename `<pf-text-area>` to `<pf-v5-text-area>`

[bennypowers]

Summary

Rename <pf-text-area> to <pf-v5-text-area> and update associated CSS custom properties to use the pf-v5 prefix.

Scope

• Rename element tag from pf-text-area to pf-v5-text-area
• Rename all CSS custom properties (e.g. --pf-text-area--* to --pf-v5-text-area--*)
• Update internal class names, imports, and type declarations

Requirements

• MUST maintain feature parity with the current <pf-text-area> implementation
• MUST rename all public CSS custom properties
• MUST update HTMLElementTagNameMap declarations
• SHOULD provide a codemod or migration guide for downstream consumers