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

cli/fish/everforest-dark-hard.fish

@@ -1,4 +1,4 @@
-# Everforest color scheme for fish shell
+# Everforest dark-hard theme for fish shell
 # Generated from template - do not edit manually
 
 # Set fish colors

cli/fish/everforest-dark-medium.fish

@@ -1,4 +1,4 @@
-# Everforest color scheme for fish shell
+# Everforest dark-medium theme for fish shell
 # Generated from template - do not edit manually
 
 # Set fish colors

cli/fish/everforest-dark-soft.fish

@@ -1,4 +1,4 @@
-# Everforest color scheme for fish shell
+# Everforest dark-soft theme for fish shell
 # Generated from template - do not edit manually
 
 # Set fish colors

cli/fish/everforest-light-hard.fish

@@ -1,4 +1,4 @@
-# Everforest color scheme for fish shell
+# Everforest light-hard theme for fish shell
 # Generated from template - do not edit manually
 
 # Set fish colors

cli/fish/everforest-light-medium.fish

@@ -1,4 +1,4 @@
-# Everforest color scheme for fish shell
+# Everforest light-medium theme for fish shell
 # Generated from template - do not edit manually
 
 # Set fish colors

cli/fish/everforest-light-soft.fish

@@ -1,4 +1,4 @@
-# Everforest color scheme for fish shell
+# Everforest light-soft theme for fish shell
 # Generated from template - do not edit manually
 
 # Set fish colors