Promote layout 03 (editorial alternating) to production; remove test pages

The sub-page now uses the alternating-zones layout: hero with text-only
3-fact list, then a zone with the workbench image + Community framing, then
two paired zones for Parallel work + Coordination and Specialization +
Checks and balances.

Delete layout-tests/ — pattern chosen, no longer needed.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: rmdevpro