🎨 Update README preview image and remove documentation files

Update README preview image and remove documentation files

- Replace preview image reference from silkcircuit-preview.png to
  silkcircuit.png in README header
- Add new silkcircuit.png image asset to assets directory
- Remove docs/COLOR_PALETTE.md containing detailed color
  specifications and usage guidelines
- Remove docs/INSTALL.md containing installation instructions
  for various plugin managers
- Remove docs/THEME_ANALYSIS.md containing theme design
  philosophy and language-specific optimizations

Consolidates documentation into main README while updating
visual assets for the theme presentation.

Author: hyperb1iss

CONTRIBUTING.md

@@ -14,7 +14,7 @@
 </div>
 
 <div align="center">
-  <img src="https://raw.githubusercontent.com/hyperb1iss/silkcircuit-nvim/main/assets/silkcircuit-preview.png" alt="SilkCircuit Theme Preview" width="90%">
+  <img src="assets/silkcircuit.png" alt="SilkCircuit Theme Preview" width="90%">
 </div>
 
 ## 🎭 Overview