feat: enhance install script and theme generation

- install.sh now installs all variants when run without parameters
- preserve single-variant mode when --variant is specified
- add variant names to generated file headers for clarity
- fix tool name extraction to preserve compound names like git-delta
- fix CSS variable preservation during header generation

CLAUDE.md

@@ -56,7 +56,7 @@ Core development commands for the project:
 
 ## Installation and Verification
 
-    ./cli/install.sh                      # Deploy all configs to ~/.config
+    ./install.sh cli                      # Deploy CLI configs to ~/.config
     ENGINE=docker ./verify/verify.sh      # Verify in container
 
 ## Implementation Guidelines