fix: clean up duplicate closing tags at end of showcase container in index.html

Redesign index.html into premium SAM 3 style landing page layout with floating search

Fix UI crash in index.html by guarding outputEmpty element references

Fix prediction payload serialization style for Gradio Server API

Fix example loading, file upload and ZeroGPU compatibility

redesign

minimal redesign

redesign

Fix programmatic file load activeFile reset bug in index.html

Convert to gradio.Server with premium custom HTML/CSS/JS frontend