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/mkdir.fish

@@ -0,0 +1,10 @@
+# Copyright (C) 2026 Rootiest
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+function mkdir
+    if status is-interactive
+        command mkdir -p $argv
+    else
+        command mkdir $argv
+    end
+end