Modernize OpenGL examples and add two shader motion studies

[daitomanabe]

Summary

• Modernize all six historical examples to ofApp, GLM, member-owned state, and programmable OpenGL 3.2 mesh rendering. Keep the existing addon API and historical authorship/license notices.
• Add Motion Ribbons, a real vertex / geometry / fragment shader study, and Motion Field, a joint-driven full-screen fragment shader study.
• Share the original A/B/C motion data; document recentering and the distinction from the original stage formation.
• Add teaching READMEs, actual rendered previews, relative Xcode projects, and deterministic rendering checks with PNG/log artifacts.

Verification

• All eight applications built in Release using Make and Xcode with openFrameworks 0.12.1 on macOS.
• All eight passed real OpenGL rendering checks. Legacy examples verify hidden/unfocused windows and changing artwork; the new studies also check shader linkage, pause/reset behavior, and a second motion timestamp.
• BVH and marching-cubes regression suite passed; all eight Xcode project structures validated.
• Malformed shader and shader-link mismatch tests fail without a success marker.
• Workflow lint, staged diff checks, and local-path/privacy checks passed.

CI separates macOS build/regression coverage from Linux Mesa/Xvfb rendering.
Hosted macOS runners cannot provide the required NSGL pixel format; local macOS
rendering is verified, and CI must render all eight applications with an actual
software OpenGL context rather than skip rendering.

Original full audio is not bundled; historical examples use the documented silent-clock fallback when it is unavailable. This update does not claim to validate unavailable original audio assets.