Keep the Panel configuration preview visible in SimpleKCM's header while options scroll. Avoid a redundant identity only when the selected provider is the sole visible meter, preserving identity for independent text among multiple providers.

Add an isolated OpenGL matrix and CI gallery for all content combinations and targeted layouts. Update usage, settings decisions, contributor documentation, and Unreleased notes; existing configuration and CLI contracts are preserved.

Validation: 895 Qt tests, 67 Python tests, strict make check, make package, 464 local captures, 336 CI matrix captures, graphical smoke and CodeQL passed. Codex found no issues; CodeRabbit's optional lint suggestions do not represent repository gate failures.