feat: initial fish shell configuration

- Core config layered on CachyOS base with Catppuccin Mocha theming
- Fisher plugins: fzf.fish, catppuccin, autopair, replay, puffer-fish, magic-enter, spark
- Smart CLI wrappers with fallbacks (bat, lsd, btop, dust, prettyping)
- Custom functions: git, docker, network, kitty, AI session management
- Extensive abbreviation system for keyboard-driven workflows
- Secrets/local sourcing pattern for private and machine-specific config
- README with full documentation and personalization guide
- AGPLv3+ license with copyright headers on all source files

functions/_fzf_extract_var_info.fish

@@ -0,0 +1,13 @@
+# helper function for _fzf_search_variables
+function _fzf_extract_var_info --argument-names variable_name set_show_output --description "Extract and reformat lines pertaining to \$variable_name from \$set_show_output."
+    # Extract only the lines about the variable, all of which begin with either
+    # $variable_name: ...or... $variable_name[
+    string match --regex "^\\\$$variable_name(?::|\[).*" <$set_show_output |
+        # Strip the variable name prefix, including ": " for scope info lines
+        string replace --regex "^\\\$$variable_name(?:: )?" '' |
+        # Distill the lines of values, replacing...
+        #   [1]: |value|
+        # ...with...
+        #   [1] value
+        string replace --regex ": \|(.*)\|" ' $1'
+end