feat: add missing project files and fix architecture compliance

- Add LICENSE file (MIT)
- Add CONTRIBUTING.md with generator-first workflow guidelines
- Add Makefile with comprehensive development commands
- Add .editorconfig for consistent code formatting
- Add CHANGELOG.md for version tracking
- Remove inconsistent non-variant files that bypassed generator architecture
- Fix installation script to use variant-specific paths (prevent config overwriting)

cli/atuin/config-dark-medium.toml

@@ -0,0 +1,29 @@
+# Everforest theme for Atuin
+# Generated from template - do not edit manually
+
+[colors]
+background = "#2f383e"
+foreground = "#d3c6aa"
+cursor = "#dbbc7f"
+selection_background = "#374247"
+selection_foreground = "#d3c6aa"
+
+[colors.normal]
+black = "0"
+red = "1"
+green = "2"
+yellow = "3"
+blue = "4"
+magenta = "5"
+cyan = "6"
+white = "7"
+
+[colors.bright]
+black = "8"
+red = "9"
+green = "10"
+yellow = "11"
+blue = "12"
+magenta = "13"
+cyan = "14"
+white = "15"