README and Showcase Dashboard Refresh

This release contains no runtime rendering changes.

v1.4.1 focuses on documentation, onboarding, screenshots, and showcase dashboards for the new v1.4 visualization system.

Added / Updated

• major README restructuring
• new Rendering Modes section
• expanded Needle Mode documentation
• new baseline telemetry examples
• additional needle screenshots for all major fill styles
• new dense telemetry showcase cards
• improved semantic fill explanations
• improved migration and configuration guidance
• refreshed screenshot dashboard
• updated playground examples
• improved showcase assets and README imagery

Now you have no excuse anymore to build that pretty dashboard. Go forth and look cool. (Or let me know if you need help.)