Release v4.12.0

Added

• Platform-neutral command form geometry metadata for columns, field placement, spans, gaps and typed width units, with JavaScript and .NET model parity. (part of #73) (part of #75)
• Command form layout validation, defaults, legacy width-token migration and resize/placement draft helpers that keep invalid draft geometry separate from committed metadata. (part of #74) (part of #75)
• Dirty command value preservation helper for metadata edits and query refreshes. (part of #75)
• Native command form rendering for typed geometry, including valid submit behavior and invalid geometry blocking before the native submit boundary. (part of #73) (part of #75)
• Command form geometry reference documentation for downstream Screenplay, Stage and Studio consumption. (part of #73) (part of #74) (part of #75)